Author Topic: Electric Fence Zapper  (Read 174246 times)

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Offline oztules

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Re: Electric Fence Zapper
« Reply #15 on: December 02, 2012, 02:09:33 pm »
Been busy, so will be later.... I use linux, so this runs under wine emulating windows.
I'm surprised your windows can't run it under properties, and then what version of windows to drive it as.... but I don't use windows, so I haven't tested it  either.

There is a free evaluation of the latest version here   http://live.altium.com/#software
Altium is a name change from protel..... at over 5 grand.... gee it's cheap isn't it......but the trial is 30 days, and is free. Don't know how big it is.

If you get on the net and search for "protel 99se download",  you will come up with something as well. There will be some unsavoury sites with cracks as well I suspect ;D


...................oztules
Flinders Island...... Australia

Offline MadScientist267

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Re: Electric Fence Zapper
« Reply #16 on: December 02, 2012, 04:00:15 pm »
Oh man.. feel sorry for ya, one bad OS to an even worse one.

LOL  ;D 

I can only imagine...

No seriously, I can ONLY imagine.  :P

Steve

Wanted: Schrödinger's cat, dead and alive.

Offline oztules

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Re: Electric Fence Zapper
« Reply #17 on: December 02, 2012, 04:53:36 pm »
Ok,
I have scribbled out a quick circuit that should be right.... :o

1692-0

The oscillator can be anything you chose if you don't want to wind a feedback style transformer, but I  find it is bullet proof and rugged., mine use larger transistors, (up to tip31 etc) and can draw an amp or so.... it is completely flexible in this circuit.... it just has to oscillate, and make the current you need for the storage you want in the time constant you choose.... I generally go for 1 second pulses... but more is fine, less may be illegal for your country (it is here).

The 640R and the 2k2 can be changed to suit your current requirements, as can the npn transistor. For your project it could be a TO92 size, drawing only a few ma to an amp or so.

The 50uf cap is about the smallest I use for larger fences, but for your size, even 2-4 uf will be fine, and this will allow your current from the oscillator to be small, (TO92 and higher values for the resistor bridge etc.)

Note the start and finish of the windings in this transformer..... otherwise it won't oscillate. (the dots are the starts).

We then rectify  the secondary, and it drives the capacitor. It should be that it takes about a second to drive the caps voltage up to around 500-600 volts.

We then use the 1m 1m 1m 330k divider to get a sample of the voltage, the variable resistor is just to get the timing better, and the finish trigger voltage more precise, but is unnecessary really. The .7uf capacitor is just to load the divider, and  so also controls the timing. If this is too big, the real (big)  cap voltage will possibly overshoot, as the voltage is not a true reflection of whats happening to the main cap, it is slightly retarded, but stops false triggers.

When the voltage across the .7uf gets to the breakdown of the diac, it triggers the triac/s.

The triacs short the storage capacitor across the transformer primary, which for me is about 9 turn 2 in hand of 1.8mm wire. This presents a very heavy low impedance load on the cap and triacs. It is this impedance that will dictate the pulse width and shape. I use about  20 turns around a ferrite, or whatever takes your fancy to impede this current flow some, and so widen the pulse. This helps in transmission over long distances, as the spike is not so high, and a bit broader, it also suppresses RF  Interferance... which over here is no bother.

It also helps keep the avalanche currents down a bit in the triacs. I used to use very expensive scr or triacs of the 50 to 100 amp range at 1200-1500volts, but found a bank of 20 cent traics of the 800v 16 amp variety to be every bit as good..... if you have a bit of inductance in the line ( the 20 turns etc).

This impedance lowers the output voltage by a good deal, but the two 2uf capacitors across the transformer fixes this up (smaller for you), and actually improves it a touch.
The diodes on the tranny are just to stop the back emf from the coil, which is necessarily savage. They need to have a 1000v rating and good surge current for big systems, and not that exciting for smaller units.

The main output transformer for me is a microwave rewound, you may find for your small fencer a normal power transformer with 110v:10v windings will do.. if it can be stopped from internally breaking down...other wise wind your own around any core you can get hold of.

In truth, you can wind it around just the "I" of a big transformer... ie an open inductor, and it will work just as well. The transformers are driven so deeply into saturation, that most of the core is seen as air gap anyway ;D .... so using air instead of the rest of the "E"'s will make very little difference in practice.

Questions or comments?


...............oztules
Flinders Island...... Australia

Offline Janne

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Re: Electric Fence Zapper
« Reply #18 on: December 02, 2012, 06:00:59 pm »
Oztules' schematic looks pretty much (in principle) like the commercial zappers I've tinkered with. Only think I might add, is that the ones I fixed always had a bank of MOV's on the secondary side, to eat the energy pulse in case nothing was touching the fence. Not sure if that's really important in practice.
Beyond the wolf border

Offline oztules

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Re: Electric Fence Zapper
« Reply #19 on: December 02, 2012, 10:36:24 pm »
Yes, without the inductor and capacitors on the primary, the spikes can be pretty impressive.

With the inductor and the caps, it makes the waveform a tiny bit more reasonable, and the rate of change of the voltage spike is slower, and so the transformer behaves a bit more like a transformer, and less like an ignition coil..... so the story goes.

In previous years, the voltage max for this country was only 5000v, and then you did have to protect the unloaded value to stay under the limit and still intimidate the cows, now that has been raised to 10000, it is not so hard to limit to less then 10000v without a string of mov on the outputs, and still have a good loaded working voltage of around the 6000v mark....... one more advantage of low impedance fencers with big (physically) out put transformers with thick wire.

Most (big ones) now have output sampling, to throttle back the output, and don't need mov's to hold them back if they are going to push the limits a bit.


Depends how sexy you want to be I guess.

I have taken to using MOV across the output triacs and the damping diodes, and even the cap.... just in case I lost the transformer, as the oscillator voltage can go very high (>1000v), and this could wreck the triacs etc.... but now I use the cheapies, I'm not so concerned..... and it seems not to have happened anyway.... still mostly use them anyway now... I have a bag full to get rid of.



..................oztules
Flinders Island...... Australia

Offline MadScientist267

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Re: Electric Fence Zapper
« Reply #20 on: December 03, 2012, 04:29:44 am »
I have a couple quick questions about this thing...

You mention tens of amps @ thousands of volts... How is this happening? I get the GIGO thing happening with the output transformer, but you're talking thousands of amps being dumped by the triacs into the primary from some caps that are in the 50uF range, give or take. What gives? Can they really supply all that, even if it is in a zillionth of a second?

The other is, 10kV @ double digit currents... How is this just a warning shot and not straight up lethal to it's victim? There's little doubt that at those voltages,  flesh approaches good conductor status, and so the current would most certainly flow. One can't help but wonder then... Is it skin effect from the pulse being so short?

Oh, and in the schematic, you show a PNP... text calls for an NPN... I'm inclined to believe that the circuit uses an NPN for the simple idea that negative ground isn't conducive to PNP operation when the emitter is on the negative side. Just figured I would mention it... I could be missing something I suppose. :)

Very nice device and layout once I got deep enough into it to wrap my whole head around it.

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline oztules

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Re: Electric Fence Zapper
« Reply #21 on: December 03, 2012, 09:34:05 am »
Yes it's true... hard to believe, but true.
I use the Gallagher fence tester ( as does most of the world I guess), and it only specs up to 14000v and 35amps.
I'm sure when I have had it maxed out at 40A, it was a bit more than 40A (it actually tops out at 40A)

http://www.gallagher.com.au/common/download.dam.document.aspx?docid=23381&filename=3C2539-SmartFix-in-volt-meter-mode-User-Manual&internal=true&extn=.pdf

I'm afraid with the low impedance fencers, these figures are not unusual...
A "normal" fence on a farm will be around the 6000v@25A under reasonable load (grass load), this would probably be a 200-300 ohm fence. With wet weather, this may climb up to 35-40 amps at a lower voltage... depending on the out put impedance.... it may drop to 4000v even..

It is simply a matter of TIME that the energy is expended in. If you can provide a good enough low impedance (true zero) path to get the time down to infinitely small, the power is infinitely large for any energy at all.... and everywhere in between.  At the discharge times were talking about (10^-7 to 10^-6 for one pulse) your up in the MHZ range .....and thats before the harmonics start....
So
"One can't help but wonder then... Is it skin effect from the pulse being so short?"............ I think so too.

Both for the power produced, and the damage inflicted on the animal. If you keep the pulse very small, the nervous system won't see it as lethal for a one off (skin effect helps here), hence the government rules.  However, multiple hits can still result in disorientation and even death  if trapped for a decent period... that why barbed wire is ILLEGAL in any form with any electric fence, and why there must be at least a second between pulses so you can get the hell out of trouble.

Yes, if you look at the transistor it should be an  NPN.... the feeble 5 min circuit indicates otherwise... probably a hanging offence over there, here I tend to always get it wrong.... I keep thinking it denotes electron flow in the real world, but it is in the conventional current world that dictates the arrow direction.... and I will never ever get used to conventional current. Why we still use a convention where the electrons/current flows from positive to negative bewilders me.....maybe thats why I'm the village idiot.

Even though it is a single DC pulse, it acts like AC in it's propagation too, including nodal points along the fence where the voltage at the end and in places in between, will show higher potential than the source. The inductance and capacitance of the fence all play a part too.

Or you can just hook it up and measure what happens.... I'm not smart enough to be able to guess the nodes and behaviour to any useful degree.



..................oztules
Flinders Island...... Australia

Offline madlabs

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Re: Electric Fence Zapper
« Reply #22 on: December 03, 2012, 10:35:21 am »
Yeah, outta the frying pan and into the fire, going from vista to 8. Not looking forward to it. Bummer is that laptops can be tough to stuff an older OS into but if 8 is bad we'll see.

Oz, schematic looks good. NPN/PNP error noted. I'm off for my 2 day shift so I can't play with things but I can read the forums.

I really appreciate the effort! If you are ever in Albion about 5 years from now (when my trees should be producing fruit) I'll buy ya a glass of hard cider! ;-0

Jonathan
Some people are like a Slinky - not really good for anything, but you still can't help but smile when you shove them down the stairs.

Offline MadScientist267

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Re: Electric Fence Zapper
« Reply #23 on: December 03, 2012, 11:45:49 pm »
Interesting...

I guess it's best then that I never went on with my ignition coil system for cars... Not for the engine, but for the idiot trying to steal my stereo...

I used a capacitive coupling to the ground, or should I say attempted... It never did couple well (for reasons I wouldn't understand until much later in life)... But it would zap the $#!+ out of you if it was parked in grass haha

I would be willing to bet the whole thing was highly illegal, and having tested it myself, I can see why. There was speculation even back then as to whether or not it was a "good idea" haha

My answer to that was "Stay away from my car and you never have to find out" :)

If I would have built something like what you have here, I'd be sending this response (somehow) from prison thanks to a most certainly impending manslaughter charge.

The stereo was a "curiosity" to say the least, but that's another thread entirely...  8)

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline madlabs

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Re: Electric Fence Zapper
« Reply #24 on: December 06, 2012, 10:28:33 am »
Oz, All,

Gotta start the *ugh* transfer over to new laptop and then I have a couple of days worth of storm damage to deal with and a car that got water under the hood and won't start. Hopefully should be able to get to starting the new zapper this weekend. Looks like I have or can salvage everything I need for it. My 5 watt panels arrived, packed crappily but intact. They look pretty good, quality wise.

Some people are like a Slinky - not really good for anything, but you still can't help but smile when you shove them down the stairs.

Offline zartoop

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Re: Electric Fence Zapper
« Reply #25 on: February 16, 2013, 06:03:24 pm »
Oztules thanks for all the great info and experience. I hope you can help me a little more with this please.

I want a system that WILL burn vegetation. I am using this on a private building to keep wall creeper under control around windows, doors and eaves.

I can either have two wires (+ve and -ve) or one wire with earth stake.

My test setup is two wires 2500mm long and spaced 25mm fixed to a brick wall. When creeper has grown between the wires the resistance is about 12K. With no vegetation between the wires it is open circuit. I have not measured the resistance of each wire to earth.

Turning one wire into a "hot wire cutter" works but the power required is impractical for a whole building as it needs about 300w just for one wire 2500 long.

I have done quite a couple of tests with various setups but none have done the job. All testing has been with 2 wires and when grown over. I have not done any tests "as the creeper grows" as the systems I have tested are too dangerous to leave on all the time.

Tests done
Flyback transformer. Arcs over in air at 10mm and pulls 20mm sparks on the bench. Driven at 20kHz / 90% duty cycle 12v primary. Will not burn vegetation when grown over. Too little current I suspect and transformer type does not handle loading?
Neon sign transformer.
10000v 30ma. Will not burn vegetation when grown over (12K). Too little power?
Hot wire
Works fine but impractical.
MOT
Haven't been game to try this as yet:)

I would like to try a Weedchopper/Weedburner type electric fence but can't find any circuits. Apparently the old Weedburner type fences were classed as 'high impedance' but this seems in contradiction to some of your previous posts.

Anyway ... Do you have any recommendations / advice please?

Offline oztules

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Re: Electric Fence Zapper
« Reply #26 on: February 16, 2013, 06:41:38 pm »
1 wire and an earth stake will do fine.

Just the simple circuit I have given here will easily do what you want.

If you want a 110v or 240 volt system, you will need to just use a doubler for the 240v unit, and a small step up for the 110v, or quadrupler circuit to get up in the 500-600 volt arena.

The only thing that you need to look at is the trigger as shown and explained, .... if you store charge into a big electro, and discharge it into a low impedance transformer, your gonna do some damage to some plants... for sure.

That one shown will burn grass off a 30km fence.

There is no magic, just simple physics.

If you have specific questions i will try to help.

..............oztules

Flinders Island...... Australia

Offline David HK

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Re: Electric Fence Zapper
« Reply #27 on: February 18, 2013, 06:05:08 pm »
Fed up with ring neck doves crapping on my BBQ table which is immediately below a mango tree.

I am planning to install a wooden pole horizontally in the tree roughly where the doves like to perch. The pole will be fitted with two x bare 1.6mm copper wires about 12 mm apart. One wire will go to battery ground and the other to my home made car ignition coil type electric fence machine HT output.

In theory the doves will stand on the pole and their feet should short circuit the HT and Grd wire. The resultant effect should be Mach 4.8 doves VTOL and a couple of feathers.

Can anyone see any technical problems with this?

David in HK

Offline DBCollen

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Re: Electric Fence Zapper
« Reply #28 on: February 18, 2013, 06:59:37 pm »
be much neater to see them burst into flames when they land
Dustin.

Offline David HK

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Re: Electric Fence Zapper
« Reply #29 on: April 03, 2013, 03:10:37 am »
Oztules,

I am interested in your circuit but the one shown above is hard to read. I have spent an hour trying to redraw and name it. Could you please take a look at the drawing and note up any details I have missed or got wrong. Thank you.

Regards,

Dave in HK