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VK6BE > TECH 10.08.04 16:01l 52 Lines 2958 Bytes #999 (0) @ WW
BID : E40478VK6BE
Read: GUEST OE7FMI
Subj: Re: 12V Cow Fence for /P
Path: DB0FHN<DB0RGB<OK0PPL<DB0RES<ON0AR<VK6HGR<VK6BBS<VK6ZSE<VK6TJ<VK6JY
Sent: 040809/1222Z @:VK6JY.#ALY.#WA.AUS.OC #:40645 [Albany] wFBB7 $:E40478VK6B
From: VK6BE@VK6JY.#ALY.#WA.AUS.OC
To : TECH@WW
The first electric fences I saw were in the farming areas in this state in
the 1930s. They worked pretty much as did the points-capacitor-sparking
coil system in pre-electronic-ignition cars. There was a coil which was
fed with 6 or 12 VDC from a car battery, and the "points" were attached to
a drumlike device which could spin through a few degrees around an axle.
On starting up the drum was kicked around a few degrees opening the
points, and then returned closing the points again. The result was a
pulse of some thousands of volts at a milliamp or two into the fence wire
from the high voltage from the coil. The impulse thus caused then kicked
the drum away again and so the cycle continued. I would say the pulses
would have been about 1 second apart.The ticking noise mentioned by Ian
was the making and breaking of the points.There could have been an auto
type capacitor in the circuit too but I can't remember whether there
was.Incidentally I heard from a farmer who said that his cattle listened
for the ticking noise and wouldn't go near the fence if they heard it. If
the noise stopped they pushed on the fence!
These fences gave a pretty hefty belt to anything or anyone who touched
the fence. I boarded on a dairy farm when teaching in a dairying area in
this state and used to help the two young fellers from the farm with the
milking. You had to be very careful which metal objects you touched. It
paid to check for wires from the electric fence before turning on the tap
on the milk vat or touching the cream separator!
I have since had experience with a modern electric fence which is
transistorised. It is a unit about the size of a small caravan or boat
type fire extinguisher. It takes type D torch batteries and the
discharging end has a metal hook which is hung on the fence wire. There is
also an earthing lead with a croc. clip which is clipped onto an earth
stake, in my case a steel fence post. The reason I got this was my border
collie dog who would not stay home. No matter how many times I repaired
the fence he would manage to get out. He dug under it, he climbed over it
and he pushed through it until at last in desperation I got this electric
fence unit and set up the wire along the places where he could get out.
He watched me do it and then I watched while he went up to investigate. He
put his nose on it and let out a yell that could have been heard a mile
away. That fence has been turned off for two years now and the dog still
won't go near it!! One case where man was smarter than the dog!
In this state too electric fences are not permitted on street frontages.
Mine was a back fence where there was only a horse paddock.
Bob VK6BE.
>
> Technically. I was raised in a farming area where they were common. You
> could hear them ticking and, as John says, it was roughly every 2 - 5 s.
> However, they didn't contain transistors so how did they work?
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