# inductor fence charger question, please

Discussion in 'Electronic Basics' started by HC, May 9, 2007.

1. ### HCGuest

Hey, all, I have about 4 of my 5 acres fenced to contain my dogs (I
have to keep them fenced since someone, I don't know for sure who,
around here shoots dogs). I have fenced most of my 5 acres so they're
not just in some little pen but they kept digging out. To deter that
I have installed an electric fence around the perimeter, a few inches
above the ground and about 6 inches in from the pen so they cannot dig
under the fence without hitting it. Unfortunately, it's a low-powered
fence charger and grass and weeds grow into it and seem to short it
out, nullifying it's effectiveness and the dogs have been able to dig
out in a few places. I would like to use a more powerful fence
charger and it occurred to me to try to build something homemade
instead of just throwing money at a more expensive/powerful charger.

Back in an electronics class I took in college we used a 12 volt power
supply and a small inductor in a simple circuit that passed current
through the inductor, through a load of some kind and then, when we
broke the power supply to the circuit, the inductor would cause a
spike back through a different portion of the circuit and would light
a small bulb (I don't know what they are called; they have gas of some
kind in them (not LEDs), with two sticks for electrodes, no
filament). The thing would flash that light very briefly but very
brightly, something that the original 12 volts could not do on its
own. The idea they were trying to point out was how an
electromagnetic field could form around a conductor when electrons
(current) passed through it and how much it could amplify the voltage
when that field collapsed.

So, I'm wondering, could I use a similar circuit (how do I build
that? It's been 15 years since I took that class.) to make a homemade
fence charger and use a coil from an old car as the inductor? That
should be good for 10-15k volts I would think, low amperage, and only
momentary stimulus. Should be enough juice to burn through weeds and
grass, and if it hits only about once a second or maybe twice a second
it shouldn't do anything to the dogs but convince them not to touch
it.

I'm only saving maybe a hundred bucks by doing it myself, but I'll
feel pretty good about myself if I do it. I can handle some simple
stuff like a 555 timer to run a relay to switch the load and some
other simple electronics. Can I make this work? Is there some better
way (short of buying an off-the-shelf solution)?

Thank you for your time and help.

--HC

2. ### HCGuest

Hmm, I found an article that I had missed earlier here:

That seems to discuss what I'm looking for.

I'm sorry. But if you happen to have more to add to that please do.
Thank you.

--HC

3. ### Rich GriseGuest

Train the dogs to stay home.

Good Luck!
Rich

4. ### Doug MillerGuest

So get a higher-powered charger -- such as one designed for use with cattle.
Any farm-and-feed store will have them. End of problem.

5. ### Eric R SnowGuest

Even though I can't help with the fence charger I do want to say
thanks for keeping your dogs on your own property. I live in a rural
area and I see dogs running loose all the time. They get into the
garbage and they kill the chickens. Then they get shot or poisoned or
run over. Either by accident or on purpose. And it's the dogs that pay
for their owner's irresponsibility. So thanks again for keeping your
dogs confined to your property, they will live longer and be happier.
Cheers,
Eric

6. ### Ross HerbertGuest

I think that unless you can prevent the weeds from coming into contact
with the conductive tape then substitutiing an even more powerful unit
will not solve the problem. The higher voltage from a more powerful
unit will break down any resistance via the grass even better than the
low power unit so it isn't going to help.

7. ### Bob MastaGuest

You might want to consider the "invisible fence" type of system, where
the dog gets shocked through its collar if it passes over a buried
wire. Seem to work really well. The only downside is that if the dog
bounds over the line (chasing a squirrel, say) the deterrent shock
also deters from getting back in.

Best regards,

Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator

8. ### Doug MillerGuest

For five acres, that's going to get really expensive.

Best solution to the problem is a more powerful fence charger. There are units
made specifically for burning through grass and weeds that grow up into
contact with them.

To the OP: repost your question in misc.rural and see what kind of suggestions
you get there.

10. ### Paul E. SchoenGuest

You might want to post also on rec.pets.dogs.behavior. I've gotten advice
there, good and not so good, for me and my dog Muttley. Watch out for the
resident troll Jerry Howe, who posts long winded tirades, under various
long nyms. My dog and I have a "reputation" there as well. I documented the
early part of it on www.smart.net/~pstech/MuttleyStory.htm.

Paul and Muttley

11. ### jasenGuest

well, the wire needn't be buried, the existing fence wire could
probably form most of the loop.

otoh the with the right sort of plow you can put wires underground
(for shallow values of underground) fairly easily.