Fabricating a 9 volt counter top electrical shocker

[Armchair Bronco]

OK, I'll admit up-front that this probably *isn't* the most intellectually
challenging question posed to this newsgroup...

In any event, my last post was at "rec.pets.dogs.behavior" where I asked for
pointers to commercial products that I could place around the perimiter of a
counter (or table) to teach our 5-month-old Golden Retriever puppy to stop
jumping up. Turns out there is such a device called the "Scat Mat", but
it's WAY overpriced at $37.00 for a single 3" x 46" strip that runs off a 9
volt battery (and I would need at least 4 of them for full coverage in the
kitchen).

I figure I can rig up something myself for under $10.00...including the 9
volt battery!

So: can someone summarize what I need to do to fabricate my own "Scat Mat"
with the following spec requirements:

1. Must run off a 9 volt battery
2. Must be relatively easy to attach and remove from the perimeter of a
table or counter
3. NO RISK OF FIRE!
4. No directly exposed wires, since the puppy will have her feet and/or nose
on the counter before she learns that this is verboten behavior
5. Must be safe (relatively speaking) for kids (I have 3 young kids, ages
10, 7 and 6)

You can assume that I know how to use a soldering iron.

Thanks in advance for any advice.

 

[Armchair Bronco]

With all due respect to Phil & Checkmate, these are NOT the answers I was
looking for!

If someone makes a post to the Alternative Music alias asking for the
whereabouts of that rare "Siouxsie and the Banshees" album from 1981, he
does not want to receive a reply stating, "Dude, why are you wasting your
time listening to Siouxsie? You ought to be listening to Frank Sinatra,
instead!"

My time definitely is worth more than $7.00 an hour, but I do have several
free hours each evening to play with, and that time I bill out at the rate
of $0.00 per hour. Sometimes I spend that time building radio controlled
airplanes -- of course, I could "save" that time by buying a ready-made kit
for $200.00, but, hey, who's couting?

The only conclusion that I can reach so far is that a simple shocking device
that runs off a single 9 volt battery is beyond the capabilities of either
Phil or Checkmate to enumerate...or perhaps only the engineers at "Scat Mat"
are smart enough to put something like this together. As for the "safe for
kids" spec requirements, I meant only that it should be relatively benign
(the shock notwithstanding) should one of the kids accidentally touch it.

 

[Armchair Bronco]

Fair enough.

You articulated your case well, and unless someone else come along with a
foolproof method for jolting my Golden Retriever without shocking my kids, I
guess I need to consider forking over $50-$100 to the experts at "Scat Mat".
(I'm already envisioning a 72-page legal disclaimer document that
accompanies the actual plastic shock pad.)

The time needed to fabricate something on my own was never a consideration
(in any event, how much time could this take even in the worst case
scenario? two, maybe three hours, tops?). But safety *IS* paramount,
especially with 3 young kids in the mix. I'm surprised that a $3.00 9 volt
battery is intrinsically dangerous, even potentially life threatening, in an
application such as this, but I'll take your word for it as I'm not an
electrical engineer; even 1 in 10,000 odds are not worth the risk.

The frustrating part is that our puppy Goldie will learn to keep off the
counters after no more than 2 or 3 shock therapy sessions, which translates
to $17-$33 per session with the plastic 9 volt shrink. Maybe I ought to
look on EBay for other dog owners who have already forked over the cash for
"Scat Mats" and are now looking to unload them now that Fido has learned to
keep off the kitchen counters.

Thanks for clearing things up, Phil. I understand.

 

[Armchair Bronco]

One last thing: I made my previous post having only read through the 1st
half of your 2nd reply (that is, up to the word "Kapeesh"). This post
addresses the second half of your reply, which -- among other things --
included references to my wife's vagina.

Please don't confuse "sarcasm" with an "insult". I did employ sarcasm in my
response, but I did not insult you (or at least, I did not *intend* to
insult you). In fact, my initial reply to both you and Checkmate was no
more sarcastic than either of the less than helpful, and highly sarcastic,
initial responses I received.

When I asked for advice on how to build an inexpensive 9 volt counter top
electrical shocker it was not strictly to "save $30 bucks" [actually, it's
more like $160 bucks if I buy 4 of the pads] but also because I enjoy
building things and I assumed (mistakenly, it now appears) that fabricating
a device running off a common 9 volt battery didn't constitute rocket
science. I was also trying to be a conscientious consumer by not buying a
plastic-based product destined to have an extremely limited lifespan, only
to see it end up in a landfill within a years of its initial purchase date.

Finally, let's not confuse an informal "spec" tied to an anonymous request
for advice posted to a public newsgroups with a formalized, written
specification requiring the formalized and costly input of a Professional
Engineer.

Having said that, I do appreciate the time you have taken to
reply...although, sadly, I doubt that my wife does.

 

[Palindr☻me]

OK, I'll admit up-front that this probably *isn't* the most intellectually
challenging question posed to this newsgroup...

In any event, my last post was at "rec.pets.dogs.behavior" where I asked for
pointers to commercial products that I could place around the perimiter of a
counter (or table) to teach our 5-month-old Golden Retriever puppy to stop
jumping up. Turns out there is such a device called the "Scat Mat", but
it's WAY overpriced at $37.00 for a single 3" x 46" strip that runs off a 9
volt battery (and I would need at least 4 of them for full coverage in the
kitchen).

I figure I can rig up something myself for under $10.00...including the 9
volt battery!

So: can someone summarize what I need to do to fabricate my own "Scat Mat"
with the following spec requirements:

1. Must run off a 9 volt battery
2. Must be relatively easy to attach and remove from the perimeter of a
table or counter
3. NO RISK OF FIRE!
4. No directly exposed wires, since the puppy will have her feet and/or nose
on the counter before she learns that this is verboten behavior
5. Must be safe (relatively speaking) for kids (I have 3 young kids, ages
10, 7 and 6)

You can assume that I know how to use a soldering iron.

Thanks in advance for any advice.

What have you got in your scrap box? Any old electronic
flashguns or cameras with electronic flash? These would,
with a little modification, provide the basis for a voltage
source. Any rolls of aluminised wall insulation? That could
provide the basis for the mat. The modifications needed
would include limiting the discharge current and just
sticking the first resistor that comes to hand will not do.
That you have to ask almost certainly shows that you don't
have the expertise to take this project on - so don't.

Far safer may be a tweeter or two out of the same scrap box,
a 555/6 timer and maybe a passive IR detector or a
break-light beam detector. A good burst of near
"ultrasonic" noise should do the trick. 555s do work quite
well as touch switches too - used in conjuction with some
glass-break detection tape.

I think that you may be a little wrong and that this could
be a good intellectual challenge - however, unless you know
exactly what you are doing with electrickery it must be left
to those that do and remain theoretical rather than practical.

 

[Armchair Bronco]

Phil,

You'd be right at home on the rec.pets.dogs.behavior newsgroup.

Well-intentioned dog owners typically post an innocent enough question
("Skippy keeps pooping on the carpet and I keep scolding him, but it doesn't
seem to work. What am I doing wrong?")

Within seconds, there are at least a half-dozen canine "do-gooders" and
"know-it-alls" jumping all over the poor poster, none of whom address the
initial question but all of whom can draw from an endless fountain of
righteous indignation (just like you).

***

"It's obvious that if Skippy is crapping on your carpet you have no business
being a dog owner in the first place!"

"The reason Skippy is soiling your carpet is because you're a rotten owner!
You don't even deserve to own a fish, let alone a dog. Loser!"

"You're scolding him? That's outrageous! I'll have you know that I'm
reporting you to the ASPCA right now!"

***

So far, after a total of 11 posts to this thread, I've received only one
reply that is even worth reading: from Palindr?me, who made a number of
reasonable alternative suggestions, while at the same time underlining the
dangerousness of my initial proposal without being preachy, condescending or
crude.

Apparently, these are traits that you have not yet mastered...and probably
never will.

One last thing: I made my previous post having only read through the 1st
half of your 2nd reply (that is, up to the word "Kapeesh"). This post
addresses the second half of your reply, which -- among other things --
included references to my wife's vagina.

Well its happened... would you have prefered another
example? I thought that one would entertain those you had
been a bit off center with though.

Please don't confuse "sarcasm" with an "insult". I did employ sarcasm in my
response, but I did not insult you (or at least, I did not *intend* to
insult you). In fact, my initial reply to both you and Checkmate was no
more sarcastic than either of the less than helpful, and highly sarcastic,
initial responses I received.

When I asked for advice on how to build an inexpensive 9 volt counter top
electrical shocker it was not strictly to "save $30 bucks" [actually, it's
more like $160 bucks if I buy 4 of the pads]

buy 1 and move it...when the puppy learns. errrr.. move da
pad.




but also because I enjoy

building things and I assumed (mistakenly, it now appears) that fabricating
a device running off a common 9 volt battery didn't constitute rocket
science.

You dint know about the transformer needed and the very high
voltage required.



I was also trying to be a conscientious consumer by not
buying a

plastic-based product destined to have an extremely limited lifespan, only
to see it end up in a landfill within a years of its initial

purchase date.

Ok Ok I take it back...I hope your wifes vagina does not
snap shut.... is that better?

Finally, let's not confuse an informal "spec" tied to an anonymous request
for advice posted to a public newsgroups with a formalized, written
specification requiring the formalized and costly input of a Professional
Engineer.

A registered PE, or even just someone considered to be pro can
be sued for all he is worth for giving advice that can be seen
as bad. When a balcony collapsed at a chicago hotel about
20 years ago... structural engineers who had simply been in
the building on other business were sued for not mentioning
the visibly obvious design flaw..as PE's they had a commission
to protect the public that went beyond thier 40 hours a week
or paid contracts.

Having said that, I do appreciate the time you have taken to
reply...although, sadly, I doubt that my wife does.

No sense of humor on the issue apparently ..thats bad.
she is over stressed maybe. Take her out to dinner tell her
over candlight that you are glad nothing has snapped shut.


Phil Scott

 

[Armchair Bronco]

Thanks for the suggestions.

I actually like the idea of rigging up some kind of break-light beam
detector connected to a loud horn (or maybe even an old camera flash unit).
My daughter is very much into "spy stuff", and she recently received a "Spy
Kit" that has a crude break-light beam detector. She hooks it up to her
door to dissuade her brothers from sneaking into "Spy Central HQ". I'm sure
she'd be willing to let me borrow this for a day to two to teach Goldie to
keep off the kitchen counters.

 

[Armchair Bronco]

Raise the table higher with some cement blocks !!

?????

Thanks for the advice; I may try this suggestion if the stainless steel
guillotine I'm planning to build in my garage fails to convince Goldie to
stop jumping up.

 

[Armchair Bronco]

I'm afraid that's pretty-much the way Usenet works in just about any
group. Here's an idea that you might find more palatable: If you're
convinced that you can make the necessary conductive pads to make this
whole thing work, and it's worth the time it'll take you to do it (which
nearly everyone in this group will probably tell you you've grossly
underestimated) why not buy one of the commercially available dog
zappers, and parallel the included pad with your fabricated pads to
extend the area of coverage?

I think you're right that I've underestimated the amount of time it will
take to do this properly; realizing this, I'm not going to do anything on my
own.

I suppose I can be forgiven for not knowing much about the mysteries of
electrical engineering, but I seriously thought I might get an initial reply
like the following:

***

"Hey Armchair: this shouldn't be to hard to, but I wouldn't want to hook the
contraption up until the kids have gone to bed. If you elminate them from
the equation, then building this thing will be much easier. Anyway, here's
what you need:

* a 9 volt battery connector from Radio Shack
* 2 long strands of thin, bare wire
* a roll of electrical tape
* etc. etc.

Here's what you do: solder the strands to the battery connector outputs, and
then run the wire strands around the perimeter of the table, keeping them
within 2mm of each other but making sure they don't touch; use electrical
tape every 6 inches or so to hold down the wire; this will keep the dog from
getting tangled up in it but will still expose enough raw wire to give her a
good jolt when she touches both wires. Etc., etc.,"

***

Obviously, I don't have any idea what I'm talking about. On the other hand,
call me "Old School", but a counter top electrical shocker (provided the
kids are removed from the mix) still doesn't strike me as Rocket Science
requiring an advanced degree in EE, even if I don't understand all of the
nuiances of electrons.

 

[Palindr☻me]

the notion


enough question


him, but it doesn't


"do-gooders" and


whom address the


fountain of


you have no business


you're a rotten owner!


know that I'm


about any


If you're


make this


do it (which


available dog


pads to



The dog zapper pads are no doubt a fine wire mesh woven into a
fabric... so that there is not static charge build up... if
our gentle friend here makes his own out of tinfoil, the
capacitance effects of the tin foil/air capacitance created
could blow his fillings out.

A 15' run of a pair of aluminium self-adhesive strips, as used for glass
break detectors, measures out at 120pF (although distance apart and
substrate will make a significant difference). At 10kV, this gives a
stored charge of about one hundredth of a joule. A taser works at about
a third of a joule and about 10 joules are needed for ventricular
fibrillation. Far more important than the stored energy in the
dog-machine interface is the stored energy and capability of the source.
A fresh standard 9 volt battery is well capable of supplying over 10
joules, so the design of the electronic inverter is critical. Increasing
the output voltage to 50 kV for a well-designed unit would probably* not
be fatal but would certainly make the recipient fairly determined not to
do it again...

--

Sue

*This system would deliver twice the energy of a standard taser, if the
source had a stored energy of about a third of a joule available for
discharge. Any test volunteers?

 

[Palindr☻me]

into a


used for glass


apart and


gives a


works at about



Thanks for the calc. So those aluminum adhesive strips are
say 1/2" wide max.. and our home owner makes his pads say 6"
wide by 60" long as per some one elses suggestion to use
aluminum foil.... for a net 350 square inches.

My model used two parallel strips, so the charge is stored in the
underlying dielectric. This is a much less efficent capacitor than, say,
an expanded foam tile with foil on both sides.

15' of the glass detector tape at 1/2 an inch would be 90 sq
inches... so with our wider piece of material we are at
roughly 4.5 times the capacitance.

so its .3 joule's as you calculated for the narrow srip x
4.5 with a 6" x 60" foil pad
or 1.4 joules roughly, assuming the foil pad is the same
thickness as the foil glass break tape. Which dont think it
is.... The glass break tape is *probably 1/3 the
thickness...if it were, then capacitance would be to 4.3
joules,

The thickness of the tape is not important - the charge is stored in the
dielectric substrate - the thicker, the lower the capacitance and the
less the stored charge. By placing the two conductors side by side, edge
next to edge, the capacitance and stored charge is much less than would
be if the overlapped, with dielectric between.

So with these rough figgers we are at half the energy needed
to create ventricular contraction... to kill the kiddies the
gentleman would have to go to 5' of material from a standard
r 12" roll of aluminum foil... and thats probable, or use
reynolds heavy duty foil. that might work.




the source.

The combo would be exciting.




over 10


critical. Increasing


probably* not


determined not to



Our home owner was going to use the 9vdc direct from the
battery, putting him into the deadly device range if he used a
12" x 5' long foil pad.. (variable with foil thickness and
conductance etc... with perfect conductance a childs moist
thin skinned hand while touching a ground (faucet handle) the
energy would go directly through the heart,

No 9V isn't going to cause a shock, even with wet hands. You can stick
a 9 V battery on your tongue to test it without fatal results (although
I don't recommend it. If you have a test child, try wetting its hands
and get it to grip the probes of a multimeter on ohms... on high ranges
that is probably 9V..

With the dog unable to touch both..and not grounded. the
charge would be absorbed by his larger body mass not taking a
route through the heart...also the thicker pads on his feet
would not conduct as well...so the dog might not even get a
shock.

Parallel strips means that the dog will bridge the conductors at some
time. With a few kV, even with only a very tiny stored charge, it will
certainly feel it.

taser, if the


available for



Very interesting. thanks again.

With the right voltage and charge it will keep rats at bay very
effectively. Take two parallel foil strips glued on a plank that is
dropped across a barn doorway and connect them to a suitable low power
inverter. You can still drive tractors in and out, over the plank, and
leave the door open. Keeps the animals in and the rats out...

 

[operator jay]

Power from your panelboard will go through a faucet in order to get to the
grounding system and back to the panelboard. Power from a battery has no
interest in a faucet because there is no path back to the battery that way.

 

[Don Kelly]

Thanks for the calc. So those aluminum adhesive strips are
say 1/2" wide max.. and our home owner makes his pads say 6"
wide by 60" long as per some one elses suggestion to use
aluminum foil.... for a net 350 square inches.

15' of the glass detector tape at 1/2 an inch would be 90 sq
inches... so with our wider piece of material we are at
roughly 4.5 times the capacitance.

so its .3 joule's as you calculated for the narrow srip x
4.5 with a 6" x 60" foil pad
or 1.4 joules roughly, assuming the foil pad is the same
thickness as the foil glass break tape. Which dont think it
is.... The glass break tape is *probably 1/3 the
thickness...if it were, then capacitance would be to 4.3
joules,






So with these rough figgers we are at half the energy needed
to create ventricular contraction... to kill the kiddies the
gentleman would have to go to 5' of material from a standard
r 12" roll of aluminum foil... and thats probable, or use
reynolds heavy duty foil. that might work.


the source.

The combo would be exciting.



Our home owner was going to use the 9vdc direct from the
battery, putting him into the deadly device range if he used a
12" x 5' long foil pad.. (variable with foil thickness and
conductance etc... with perfect conductance a childs moist
thin skinned hand while touching a ground (faucet handle) the
energy would go directly through the heart,

-------------------
There is something wrong here. While a 9V battery may be able to supply 10
Joules- it won't be able to do it at once or even in a few seconds. In an
hour, maybe-what is the short circuit current of such a battery and how long
can it be maintained? Otherwise there would have been a lot of people
killed by 9V batteries (how many have licked the terminals?- tastes funny
and may tingle).

Secondly, 120 pf for side by side tapes- laying wider tapes will not make
much of an increase of the capacitance between them, unless one is over the
other, separated by some dielectric. In that case one side will be on the
floor and it would not serve the purpose as a dog zapper. The zap comes from
contact with both plates.

Now suppose we do scale up the size as you indicated from the original
120pf, 90 sq.inch tape to 12"=60" 720 sq in. so the capacitance is now just
about 1 nanofarad. Lets make it 10 nf as the foils are close together. Now,
at 9V the energy stored will be 0.5*(10^-8)*9*9 =0.4 microjoules.
This is probably not even noticeable ( a spark discharge of 1000 times this
energy is classified as painful, but harmless).

Palindr?me was talking about 10kV, not 9 V. In that case the stored energy
would be about 0.5Joules.
------------------

With the dog unable to touch both..and not grounded. the
charge would be absorbed by his larger body mass not taking a
route through the heart...also the thicker pads on his feet
would not conduct as well...so the dog might not even get a
shock.

-------
If the dog was unable to touch both and is ungrounded, the dog will not
absorb any charge from the device even if he peed on his feet. . He hasn't
completed a circuit to discharge the capacitor.
--
Don Kelly
[email protected]
remove the urine to answer

----------

 

[Palindr☻me]

-------------------
There is something wrong here. While a 9V battery may be able to supply 10
Joules- it won't be able to do it at once or even in a few seconds. In an
hour, maybe-what is the short circuit current of such a battery and howlong
can it be maintained? Otherwise there would have been a lot of people
killed by 9V batteries (how many have licked the terminals?- tastes funny
and may tingle).

Nothing wrong, an inverter circuit would need to charge a
capacitor for some time in order to transfer the charge from
the battery. Think of the time it takes to get the "ready"
light up on a camera flash and multiply by the number you
first thought of..

Secondly, 120 pf for side by side tapes- laying wider tapes will not make
much of an increase of the capacitance between them, unless one is overthe
other, separated by some dielectric. In that case one side will be on the
floor and it would not serve the purpose as a dog zapper. The zap comesfrom
contact with both plates.

Actually, you normally want to minimise the capacitance and
hence energy stored in the output interface rather than
within the unit. The energy stored within the unit is
pre-determined and can be designed precisely for - unlike
the output interface. With the unit output floating, the
output interface actually comprises two capacitors in
series, with the ground plane acting as the link between the
two. This, of course, reduces the voltage on the strips to
ground over a single conductor and minimises "side effects".
The zap normally comes from proximity to the strips - actual
contact is not needed.

Now suppose we do scale up the size as you indicated from the original
120pf, 90 sq.inch tape to 12"=60" 720 sq in. so the capacitance is now just
about 1 nanofarad. Lets make it 10 nf as the foils are close together.Now,
at 9V the energy stored will be 0.5*(10^-8)*9*9 =0.4 microjoules.
This is probably not even noticeable ( a spark discharge of 1000 times this
energy is classified as painful, but harmless).

Palindr?me was talking about 10kV, not 9 V. In that case the stored energy
would be about 0.5Joules.

The dog merely need to get close to the two strips - the
voltage present will do the rest. Grounding is not needed -
but half the voltage will be present between either strip
and ground - with the two capacitors formed by the strips,
their underlying dielectric and the ground surface on which
it is resting. Only the energy stored in the output device
capacitance (approximately, the inverter will add some
additional energy) from one strip to ground will be
discharged - a "warning" tingle, perhaps?

 

[Palindr☻me]

OK, I'll admit up-front that this probably *isn't* the most intellectually
challenging question posed to this newsgroup...

In any event, my last post was at "rec.pets.dogs.behavior" where I asked for
pointers to commercial products that I could place around the perimiter of a
counter (or table) to teach our 5-month-old Golden Retriever puppy to stop
jumping up. Turns out there is such a device called the "Scat Mat", but
it's WAY overpriced at $37.00 for a single 3" x 46" strip that runs off a 9
volt battery (and I would need at least 4 of them for full coverage in the
kitchen).

I figure I can rig up something myself for under $10.00...including the 9
volt battery!

So: can someone summarize what I need to do to fabricate my own "Scat Mat"
with the following spec requirements:

1. Must run off a 9 volt battery
2. Must be relatively easy to attach and remove from the perimeter of a
table or counter
3. NO RISK OF FIRE!
4. No directly exposed wires, since the puppy will have her feet and/or nose
on the counter before she learns that this is verboten behavior
5. Must be safe (relatively speaking) for kids (I have 3 young kids, ages
10, 7 and 6)

You can assume that I know how to use a soldering iron.

Thanks in advance for any advice.

As there seemed to be some misconception of the circuit in
question, I thought a quick restatement of the system
proposed might help:

A low voltage dc source (eg 9v battery) is connected to a dc

dc inverter and raised to some 10kV (for example). The

output of which is floating (ie neither side connected to
ground).

The two wires from the output of the inverter are connected
to two pieces of self-adhesive aluminium foil (eg as used
for break-glass alarm detectors). These strips are glued to
an insulating board (lets say a perspex sheet) running in
parallel (lets say 2" apart). The board is then placed where
you don't want animals to go, say resting on a damp (eg
conductive) surface.

Each strip will effectively be one plate of a capacitor,
with the damp surface being the other plate and the perspex
being the dielectric. The damp surface will join the two
capacitors together, to form a series circuit. The inverter
will see two such capacitors in series and will charge each
to approximately half the voltage of the inverter.

When an animal approaches, it will get one of these
capacitors discharged through its body to ground (the damp
surface). A very small amount of energy will transfer as the
capacitance is small. Some small additional current will
flow as the other capacitor will now charge to the full
inverter voltage, as one part of the capacitor series
circuit is effectively being shorted out by the animal.

It generally runs off. If it continues on, it will reach the
point where its body will bridge the gap between the two
strips. The energy stored in the inverter will be discharged
into its body at that point - plus the energy stored in the
capacitor which has been charged to full inverter output
voltage. It will have something to remember.

For larger animals, put the strips further apart. For
animals that you rather care about, put the strips much
further apart - so that they will not bridge the strips. In
the latter case, it will get a half voltage shock from the
first strip and full voltage from the second (many times the
effect). By suitable arrangements of strips, dielectric and
ground plane, you can extend this staircase voltage effect
further - to give greater and greater shocks to the animal
as it insists on advancing. Ultimately, you could have two
strips connected to the inverter, close enough to be bridged.

You could, of course, do the same thing with a voltage
divider chain much more accurately, but this isn't
appropriate for a battery driven circuit.

Hope that helps!

 

[Steve Alexanderson]

Fits all your specs but number 1. Lining the counter edge with mousetraps
did the trick with my lab. After one day we could move the traps back to the
attic, and the counter remained dog free for the rest her life.

 

[Don Kelly]

with ac thats true...with DC not always...the body can
hold a charge...it has capacitance itself as you probably know
(recall the high school static electricity build up test)

-------------------
The shape of the field and the distribution of equipotentials are the same
with AC and DC. Exactly the same techniques are used to calculate the
fields, capacitances and short circuit currents in both cases. The AC case
can be handled using of peak voltages or in terms of rms voltages-
whichever is most suitable .

There is a potential between the plates. The body is standing on top of one
plate and the field above this plate will be small. The field between the
top of the body and the plate being stood on will be even smaller.
Certainly, if one stood with ones toes overhanging the edge, said toes would
be in a fringing field (more likely would actually bridge the plates) and a
shock could be felt but this would not lead to death by electrocution or
fibrillation.

The body has capacitance but the capacitance in this case is immaterial
assuming that nothing above is at the same potential as the bottom plate.
Sure the body can be charged but in this situation there is nothing or
nearly nothing to charge it - no interchange of chargedue to mechanical
means as in the static case and little to no field in the region of the
body to charge the body electrically.

Suppose that you were in a car with a 10KV line between the car and ground,
( a known safe situation) and somehow climbed out of the window and stood on
the car's roof. Will you be in any more danger? NO. The car will have a
capacitance of about 300pf to ground and this wll be charged. You will have
a capacitance (with ordinary shoes) of about 120pf to the car roof. You are
on your own local "ground plane" even if that plane is at 10kV with respect
to the real ground. Will you feel it- even with DC? NO- but just don't let
anyone hand you a cup of coffee.

 

[Roger]

OK, I'll admit up-front that this probably *isn't* the most intellectually
challenging question posed to this newsgroup...

In any event, my last post was at "rec.pets.dogs.behavior" where I asked for
pointers to commercial products that I could place around the perimiter of a
counter (or table) to teach our 5-month-old Golden Retriever puppy to stop
jumping up. Turns out there is such a device called the "Scat Mat", but
it's WAY overpriced at $37.00 for a single 3" x 46" strip that runs off a 9
volt battery (and I would need at least 4 of them for full coverage in the
kitchen).

I figure I can rig up something myself for under $10.00...including the 9
volt battery!

So: can someone summarize what I need to do to fabricate my own "Scat Mat"
with the following spec requirements:

1. Must run off a 9 volt battery
2. Must be relatively easy to attach and remove from the perimeter of a
table or counter
3. NO RISK OF FIRE!
4. No directly exposed wires, since the puppy will have her feet and/or nose
on the counter before she learns that this is verboten behavior
5. Must be safe (relatively speaking) for kids (I have 3 young kids, ages
10, 7 and 6)

You can assume that I know how to use a soldering iron.

Thanks in advance for any advice.

A easier and safer way would be
Get a 12V motion detector with a normally open contact
Get a 30Watt Siren
Point the motion sensor across the protected area
Connect a 12 VDC power supply to the motion detector and use the motion
detector to switch the siren on.

After a few attempts of going throught the protected area the dog will
learn.

You could even get a hallway lens for your Motion Detector that would
direct the beam in a straiter line.