How to keep raccoons away

Page 5 of 7  
On Mon, 10 May 2004 20:54:32 -0400, styxx374 wrote:

Me too, Northern Tier. I did see them drive by with the bear barrel once, but I wouldn't hold my breath for them to remove anything else. http://www.pgc.state.pa.us/pgc/cwp/view.asp?aE8&q 0709
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In fact, I can remember (vividly, no less) one dusk when we were playing tag across the pasture, and I practically garrotted myself on a wire gate that I thought was open. Caught the wire (between barbs, thankfully) right under the chin, and both feet went out in front of me.. *wham* "I don't want to play, anymore."
--Goedjn
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Heh. I did pretty much the same thing years ago when I was a brand-new, shiny EMT. Responded to a car accident; the car had run off the road, through a barbed wire fence, and overturned, scattering it's un-belted occupants. Things were going really well in my getting to them, until I encountered the part of the barbed wire fence which was still intact. Nice scars, one on my upper arm, another on my chest. I didn't mention it to anyone at the scene, or I would have got that year's award at our annual party, for sure.
Fences, plus dark, plus more speed than visibility, are a bad combination.
Dave Hinz
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Somehow I doubt it's the brevity that makes static electricity harmless. I've played around with battery-powered circuits that work by delivering pulses of electricity to the subject when the current through a circuit containing an inductor is interrupted (for example, the gag lighters that shock people work this way). Whatever current is flowing through the inductor gets sent through the subject for a short period of time. It's relatively safe because the peak amperage is controlled. If you hook up a resistor in series with the subject, the maximum current doesn't change, but the pulses get shorter. When you do this, the pain falls off, but the response from your muscles doesn't change as much. Eventually, especially if the contact area between the electrodes and the skin is large, you can produce involuntary muscle contractions with little or no pain.
Given that the heart is a muscle, I would think that a few seconds of current would be better than a few milliseconds if the goal was to produce pain without rendering any permanent harm. I could be wrong, but if I had to guess, I'd say the reason static electricity isn't harmful is because most of the voltage is across the air gap, not across your body. Also, the charge is entirely on your skin, and most is probably very close to the spot where you're about to touch something, so practically no current is going through your heart.

Surely it couldn't be very difficult to have a device of some sort in the circuit to control the maximum current. At the very least, couldn't he just put an appropriate fuse in the circuit, if there wasn't one already?

There's almost one order of magnitude between the current needed to cause pain and the current that's large enough to be dangerous. The fact that the area of contact with the wire is small, and a three-year old is larger than a racoon, ought to make the range of safety even broader.
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Jim Black wrote:

Who said static electricity is harmless? Lightning is static electricity, but I don't see many people standing outside in a thunderstorm.
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Oops ... but you know what I meant -- static electricity at around 2000 - 4000 volts, as was being discussed. Practically everything is lethal if you get enough of it.
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How well I remember shuffling across the carpet & pointing my finger at my sister's head, giggling until -- FLASH! -- both of us fell into fits of tears. And that's why to this day I have but nine fingers & my sister went blind & became bald for life.
-paghat the ratgirl
--
"Of what are you afraid, my child?" inquired the kindly teacher.
"Oh, sir! The flowers, they are wild," replied the timid creature.
  Click to see the full signature.
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paghat wrote:

Did your sister become a lesbian, too?
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Curiousity got the better of me ...
Safest is a battery-powered, pulsing (as opposed to continuous) electric fence controller bearing Underwriters Laboratories label ANSI/UL69 (Electric Rence Contollers) One town's regulations specified that the current pulse a maximum of 60 times a minute with the duration of each pulse a max of 1/10 second and be 25 milliamps or less. This is on the high side; the newer controllers have pulse duration around 1/1000 second. Voltages seem to run in the 5K-7K range. The shorter pulse duration also has the advantage of not heating dried vegetation to combustion temperature.
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Most fence chargers work on pulses. You get zapped, but that's all it is...a zap. You have plenty of time to let go before it sends another pulse...and you tend to let go in a hurry.
A 3 year old would be fine with the fence...just like the cows...one zap and they develop a healthy respect for it.
jena

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"JMartin" <> wrote in message > Most fence chargers work on pulses. You get zapped, but that's all it

Very true unless you're like me. A number of years ago I kept a horse at a neighboring property, the field surrounded by an electric fence about two feet off the ground. In a small area with a lump in the ground, I would step over the fence to take a shortcut to the barn. Once, in shorts my inner thigh caught the fence. As I danced back and forth, getting each leg, I finally jumped high enough to clear it. It hurt but more of a slap/surprise kind of hurt. I must have looked so silly dancing over that fence <grin> Sue Northern Wisconsin
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As others have said, voltage doesn't kill, current does. If you want proof, go to a children's museum with a Van de Graf generator and observe as kid after kid cheats death at the expense of hairstyling. The Van de Graf Should be putting out least 10,000 V.
That said, it exceeding more likely for current to force a path through your body as electric potential (voltage) increases. So for most intents and purposes high voltage will kill you, but it also requires sustained current running through your body, screwing with your normal electrical functions and overheating your cells. (The current does not have to be high at all.) Now don't go sticking your finger in a socket or something, thinking you'll be able to let go after a short time, because you won't.
If anything, DC is "safer" than AC, but I believe this involves transmission losses that don't occur due the electric field generated by the oscillating alternating current. But the tranmission losses should be neglible at short distances and "safe" in this sense is not relevant. (Does AC make it more diffult to remove your hand from an outlet? That could be another reason, but I'm not too sure about it).
Static electricity is a capacitive discharge (as is lightning and battery power). The only difference between that and electricity from an outlet is that there is nothing resupplying the capacitor and so the duration is short, depending on the size of the capacitor. (Just because you usually get DC power from batteries and AC power from an outlet doesn't mean they can't be the other way around. It wouldn't be efficient, but you could do it).
Running electricity through a step-up transformer will step up the voltage at the expense of (I'm not sure I remember this correctly, but what else would it be?) current. (Inside a block transformer, you may also have a rectifier that converts AC to DC). You will also have current losses from the conversion and needless to say, just because you are on a 15A line, it doesn't mean the device or transformer will draw the full 15A. The input and output ratings should be printed on the transformer block. All other things being equal, the calculation above is still missing a sqrt(2) since the source is AC (in addition to conversion losses which I am guess could be 30%.)
The term "transformer electricity" should probably be reserved for Autobots and Decepticons.
[rec.gardens]
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GOTHE CHEAPY WAY
Go down to Walmart and buy yourself a few bucks worth of MOTH BALLS, yes Moth Balls. and scatter them around and all your animals will stay clear until they all evaporate in about a month then scatterer some more. If you have youngsters they might think they are candy so take that in mind.
Jack
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tinacci wrote:

Tried it. Doesn't work well in the open, where the wind can remove the smell.
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Salty Thumb wrote:

probably much more. The breakdown field strength for air is about 25000 volts/inch. Look at the length of the sparks the Van de Graf generates. Of course, the field strength from a sharp point (such as the end of a strand of hair) drops off as r squared, so the local field could generate a breakdown which could propagate.
As far as the current level goes, I have heard that it requires as little as 0.01 amps to kill a person. This is a very small current, and I suspect that it wouldn't kill an average person except in exceptional circumstances. I know people who have experienced up to 0.05 amps (DC) before reporting discomfort (they did survive to report no discomfort).
Small currents generally kill by inducing paralysis of various important muscles, such as those responsible for breathing or blood circulation.
Large currents can kill by damaging muscles or nerves.

The voltage isn't really important if you can get the current up. Normal skin resistance requires a fairly high voltage to overcome, but if you implant an electrode below the skin into a region where bodily electrolytes can conduct the current, you can probably electrocute someone with 40 volts (as long as the current is high enough).

As far as AC/DC is concerned, it really doesn't matter. For the relative merits of AC and/or DC, refer to the discussions between Edison (DC proponent) and Westinghouse (AC proponent). Westinghouse won, although there were sections of New York City that were supplied with DC power up until the late 20th century. The main reason that AC won out over DC was that AC could be transmitted over large distances by raising the voltage and lowering the current. The resistance of the wires is what causes the transmission losses and lowering the current reduces the voltage drop. Since the voltage is high, the voltage drop is less important, being a smaller fraction of the total. Both of these reasons make AC power transmission more efficient.

Static electricity, although of short duration, is sufficient to fry electronic chips, since the current is concentrated into a small area on the chip. In that case, the relevant parameter is amperes per square cm.

Correct. The power (product of current and voltage) remains the same (neglecting transformer heating).
I have not been following this thread, but suppose it to have been started by someone recommending an electric fence transformer for raccoon prevention. The electric fence transformer I used to have was rated 0.01 amperes output. I measured the voltage at 1500 volts. The AC voltage was continuously supplied as long as it was plugged in. Being normally forgetful, I neglected to unplug the system several times and did a little garden sparking. It was unpleasant, and not something I'd like to do frequently, but I believe it was just enough to discourage repetitions (and improve memory). Other electric fence systems are pulsed, so that a single spike of high voltage is presented every second or two. The time interval between pulses is quite enough to withdraw one's hand or other portion of the anatomy that came in contact with the wire.
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says... <
<snip> <I'm pretty sure it takes more than 9v to scare off a racoon. So how much <voltage would you use that would do the job but not hurt the child? I know <you can die from as little as 50v. Even less if you got imaginative. < < <
Voltage doen't kill you, current does. You get hit a lot of voltage when zapped with static electricity, but very little current.
        Bill
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know
Yes but they dont use static electricity in electric fences, do they?
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says... <
< <> says... <> < <> <> <snip> <> <I'm pretty sure it takes more than 9v to scare off a racoon. So how much <> <voltage would you use that would do the job but not hurt the child? I <know <> <you can die from as little as 50v. Even less if you got imaginative. <> < <> < <> < <> <> Voltage doen't kill you, current does. You get hit a lot of <> voltage when zapped with static electricity, but very little <> current. < <Yes but they dont use static electricity in electric fences, do they? < < <
Electricity is electricity. Lightning is static electricty, but I wouldn't want to get hit with it.
        Bill
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much
No, there's a difference. A static charge of 1000v will (in most cases) dissipate so quick you barely hear the snap, where 1000v ac or dc will kill you more than likely. Now that I think of it some, it may be that they *do* use static electricity for fences. Looked up electric fence on the internet. What I read doesnt explicitely say static charge, but they are talking about powering it with a low voltage battery so that does kind of imply a short lived charge.
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says... <
< <snip> <> <> Voltage doen't kill you, current does. You get hit a lot of <> <> voltage when zapped with static electricity, but very little <> <> current. <> < <> <Yes but they dont use static electricity in electric fences, do they? <> < <> < <> < <> <> Electricity is electricity. Lightning is static electricty, but I <> wouldn't want to get hit with it. < <No, there's a difference. A static charge of 1000v will (in most cases) <dissipate so quick you barely hear the snap, where 1000v ac or dc will kill <you more than likely. Now that I think of it some, it may be that they *do* <use static electricity for fences. Looked up electric fence on the <internet. What I read doesnt explicitely say static charge, but they are <talking about powering it with a low voltage battery so that does kind of <imply a short lived charge. < < <
Your static charge is DC. It's the same as the charge stored in a capacitor. It just happens to be created by friction instead of a battery or other mechanism. The zap you feel when you get charged up shuffling across a carpet then touching a door knob is just the electrons flowing from you to the door knob hence DC. It doesn't kill you because there isn't a lot of current flow for a long period of time.
"Ampere. The unit of electrical current. Also milliamp (one thousandth of an amp) and microamp (one millionth of an amp). One amp corresponds to the flow of about 6 x 1018 electrons per second."
So 1000v that only produces current flow for a millisecond is going to be felt, but that's about it because as soon as the current starts flowing there's nothing to keep it flowing and the voltage drops quickly. When you get hit with 1000v with a power source behind it that can keep the current flowing with out the voltage dropping your in deep doodoo.
For the sake of argument, lets say your body equals 100 ohms of impedance: 1000v /100 ohms = 10 amps but since amps are a function of current over time and current flowed only for 1 millisecond you have to divide 10 amps by 1000 and get 10 milliamp equivalent. Enough to get your attention for sure. But rarely if ever fatal.
See:     http://www.t2.unh.edu/spring99/pg4.html
for the effects of rising levels of current flow.
The fences probably use a capactive discharge circuit.
        Bill
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