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...
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.
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,
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.
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.
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.
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..
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.
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...
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.
------------------- 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.
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------- 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.
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)
Nothing wrong, an inverter circuit would need to charge a=20 capacitor for some time in order to transfer the charge from=20 the battery. Think of the time it takes to get the "ready"=20 light up on a camera flash and multiply by the number you=20 first thought of..
Actually, you normally want to minimise the capacitance and=20 hence energy stored in the output interface rather than=20 within the unit. The energy stored within the unit is=20 pre-determined and can be designed precisely for - unlike=20 the output interface. With the unit output floating, the=20 output interface actually comprises two capacitors in=20 series, with the ground plane acting as the link between the=20 two. This, of course, reduces the voltage on the strips to=20 ground over a single conductor and minimises "side effects". The zap normally comes from proximity to the strips - actual=20 contact is not needed.
The dog merely need to get close to the two strips - the=20 voltage present will do the rest. Grounding is not needed -=20 but half the voltage will be present between either strip=20 and ground - with the two capacitors formed by the strips,=20 their underlying dielectric and the ground surface on which=20 it is resting. Only the energy stored in the output device=20 capacitance (approximately, the inverter will add some=20 additional energy) from one strip to ground will be=20 discharged - a "warning" tingle, perhaps?
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.
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.
------------------- 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.
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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