Re: Electric fence effective?

quote:
Analogkid I hope to hear your views as lunatics like ourselves need somone sane to guide us.

***

OR, I can let y'all go on your merry way, and keep the deep end of the gene pool to myself....

In no particular order:

Earth battery - Last I heard, there is only one kind of "electricity". Electrons have charge and spin, and produce electric and magnetic fields. When they move, things happen. I did some reading on the earth battery. It looks like a combination of a traditional chemical battery and a 1-turn transformer winding or loop antenna. Depending on the writer, it is either a 1V, low current, relatively high output impedance (in other words, not so hot) battery, or a pickup device for circulating currents in the earth. Either way, the output current will be very low relative to its size. "Power a house" ??? Nope. Maybe a flashlight. I can't see hauling a dozen 4-foot pieces of 3" diameter copper pipe (with matching zinc rods) around Ohio, let alone Africa.

I tripped across yet another website expounding "scalar waves". Still don't make sense, and in the case of the earth battery, completely unnecessary.

Power sources - If you want to get the most out of any zapper circuit, you need to pay attention to the quality of the power source. Since a zapper tries to deliver current at high frequencies, you want a power source with a low output impedance *at those frequencies*. Almost none of the zapper schematics I've seen attend to this. Because the fix is such a simple and cheap thing, its omission gives insight into the technical skill level of the designer. We're talking about a decoupling capacitor.

In the world of circuit design - at any circuit speed - the rule of law (not thumb) is a minimum of one decoupling capacitor per chip. With higher performance chips, it is one cap per power supply pin. Even if the power source is theoretically perfect (and batteries ain't), the connecting path, be it wire or pc board trace, has inductance. This acts as a kind of resistor between the battery and the chip. Even worse, it increases at higher frequencies. This can have a direct effect on the "squareness" of the output square wave, decreasing output energy at the higher harmonic frequencies. The solution is to place a small capacitor as close to the chip power pins as possible. The cap is charged up to the voltage of the supply (usually 9V in zappers) through the wire inductance. But when the chip wants a lot of current for a very short time (less than a microsecond in the case of a 555), it can get it from the decoupling cap very quickly and at full voltage. It's like having two power sources, one there all the time and one that kicks in only for the edges of the square wave. 5 cents, visible improvement in the output. AC wall adapter, alkaline battery, solar cells, whatever - decouple the chip and the circuit will not care, and the performance will not change.

100V Zapper - bad idea. Ohm's law permutation -> R = E / I. A 100 volt source will "push" 2 milliamps through 50,000 ohms. For a constant 100V source, if the resistance is lower, the current will be higher. With a constant current source, if the resistance is lower, the current will stay at 2mA but the output voltage will sag.

I took two small sheets of aluminum, clipped my ohmmeter to them, and stood on them with bare feet. The reading wandered around a lot, but never dipped below 100K. At this resistance, you will need way more than 100V to move 2mA. I think PZ posted that real footpads and a saline solution bring this down to the 10K range. If so, now you're up to 10mA with a 100V source. That's approximately the peak short-circuit current of a traditional zapper circuit, and three times the limit set by UL. The good news is that the direct current path does not transverse the heart.

The problem is that skin resistance changes with voltage. The open circuit voltage of my DMM is about 1V at the high scale. Skin resistance has a negative resistance characteristic - rather that present a constant value rebardless of the voltage, its resistance goes down as the voltage goes up. Actually, the surface resistance of the skin itself is relatively stable; its the stuff underneath which changes dramatically in the contact area. The result is the same - ten times the voltage makes for 100 times the sensation, if not more. I have no hard numbers, but this is bad no matter how you look at it. I still remember the 90V B battery. Contacting the relatively thick, dry skin of the palm side of the index finger, I got a very respectable jolt. I would *NOT* want to feel this through the thin, damp skin of the arch of my foot.

You guys, on the other hand...

ak

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