Fabricating a 9 volt counter top electrical shocker



------------------- 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"`" 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. ------------------

------- 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
snipped-for-privacy@peeshaw.ca
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------------------- 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.
--
Don Kelly
snipped-for-privacy@peeshaw.ca
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Don Kelly wrote:

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..

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.

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?
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Armchair Bronco wrote:

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.
--

Sue





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most intellectually

where I asked for

the perimiter of a

Retriever puppy to stop

"Scat Mat", but

that runs off a 9

coverage in the

$10.00...including the 9

my own "Scat Mat"

perimeter of a

her feet and/or nose

behavior
young kids, ages

good idea. myself though Id just goose the pooch with a chop stick.
Phil Scott

practical.
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For what it's worth, we got a cat to avoid counters that it lept onto with an array of thumb tacks. Zero volts, and useful for other things after the animal is trained.
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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.

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On Sun, 24 Oct 2004 04:38:23 GMT, "Armchair Bronco"

Raise the table higher with some cement blocks !!
?????
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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.
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message

stainless steel

convince Goldie to

spring loaded or gravity?
Phil Scott

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Armchair Bronco wrote:

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!
--

Sue

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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.

for
a
9
nose
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Armchair Bronco wrote:

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.
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