Author Topic: Electric Fence Zapper  (Read 145985 times)

0 Members and 2 Guests are viewing this topic.

Offline madlabs

  • Full Member
  • ***
  • Posts: 113
  • Karma: +7/-0
    • Chief Bottle Washer
Electric Fence Zapper
« on: November 28, 2012, 08:28:59 am »
Hi All,

I'm working on a electric fence zapper to keep critters, including bears, out of my orchard. Since the zappers one can buy seem too wimpy for bears, plus what fun would it be to buy one, I decided to make one myself starting with a ignition coil. Right now I am pulling a bright 1" spark. Haven't had the guts to touch it yet, I'm scared. :)
 
So, I'd like a little help confirming that what I have designed seems reasonable. I am using a 7aH, 12V SLA battery. The coil's primary measures 1.2 ohms. The circuit uses 10mA. I am going to charge it with a 5W solar panel that has almost perfect solar exposure.

1.2 ohms = 10 amps @ 12V = 120 watts.
The circuit activates the coil every 3 seconds. This means 28,800 zaps per day.
The pulse length is 6mS X 28,800 = 172 seconds of on time per day, or .048 hours per day.
120 watts X .048 = 5.76 wH / day
10mA = 2.88 wH/day + 5.76 wH/day = 8.64wH/day total. Assuming 30% charging inefficiency, 11.23 wH/day.
7aH @ 12V = 84wH/day, so in theory 7.4 days of battery life.

Seems to me that should work out fine and have decent battery life. I will be using a simple LM317 adjustable regualtor for a charger. Since I am not using a "real" charger, what voltage should I set it at? 13.8? A little higher?

Thanks!

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 ghurd

  • Global Moderator
  • Sr. Member
  • ******
  • Posts: 442
  • Karma: +22/-0
    • GHurd Solar
Re: Electric Fence Zapper
« Reply #1 on: November 28, 2012, 11:07:10 pm »
I would use 13.8V.

If your circuit math is right, the 5W panel should keep up just fine.

Might want an LVD on it in case a shocked bear knocks in down.
G-

Offline Norm

  • Sr. Member
  • ****
  • Posts: 475
  • Karma: +26/-0
  • Today is the day you worried about yesterday.
Re: Electric Fence Zapper
« Reply #2 on: November 28, 2012, 11:17:18 pm »
to test it hook up to a cattle prod and wait for a bear to come 'round?
leap of faith !    LOL !
Norm ;)

Offline madlabs

  • Full Member
  • ***
  • Posts: 113
  • Karma: +7/-0
    • Chief Bottle Washer
Re: Electric Fence Zapper
« Reply #3 on: November 29, 2012, 09:56:18 am »
Ghurd, by LVD do you mean low voltage dropout? If so, gotta simple circuit? I am just putting together the art for the final PCB to include the charger and so could add some stuff. Although I am tempted toi make a sub board since the zapper PCB turned out so nice.

Norm, you're the one with the lightning bolt on your picture, YOU test this thing! :)

Thanks, 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 bj

  • Hero Member
  • *****
  • Posts: 735
  • Karma: +23/-0
  • Lamont, Alberta, Canada
Re: Electric Fence Zapper
« Reply #4 on: November 29, 2012, 06:27:17 pm »
One inch spark?  I'll be standing in the coward's line.
"Even a blind squirrel will find an acorn once in a while"
bj

Offline philb

  • Full Member
  • ***
  • Posts: 123
  • Karma: +6/-0
  • No Personal Text Set by User
Re: Electric Fence Zapper
« Reply #5 on: November 29, 2012, 08:28:13 pm »
A CRC book of Chemistry and Physics has a good spark table that can tell you how much voltage it takes for a 1 inch spark. 10 mA is a very hot fence charger. Most of the professional chargers are significantly less.

I would guess it is enough voltage to p**s a bear off bad enough I wouldn't want to be in the same county.

If you use a smooth wire to carry the voltage, you may want to wrap it around barbed wire or something pointed to get through the bear's fur.

I had a "Super Safe Leakage Tester" to check distributor caps, coils and wiring for cracks. It was made in the '60's. You could hold your finger an inch from insulation on the test leads and see a blue spark. It was almost all voltage and no amps so no shock. The other settings would drop the voltage and raise the amps. That would make anyone holler and end up on their knees. I never could understand why it said super safe.  :o

Offline oztules

  • Forum Advisors
  • Hero Member
  • ****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Re: Electric Fence Zapper
« Reply #6 on: November 30, 2012, 04:36:58 am »
Don't ever consider using barbed wire with an electric fence.... it is very very illegal, and downright dangerous.

Having said that, I have delved into ignition coil fencing units before, and can say they do work to some extent.
If your fence is clean, and short (around a haystack etc) they are fine.

If you wish to do any good with a loaded fence, they are useless.

It is far better to build a tiny multivibrator to change the 12v to 400-600 volts, store that in a capacitor and then discharge that into a low impedance transformer.

The ignition coils solution is a very very high impedance solution, and mostly unsatisfactory for most uses..... thats why no commercial solutions use them.

If you want a circuit for this I can provide a simple very effective board design for you. It can do up 10000 volts at 40 amps... good for a 70km- 100km of wire fence.

You will need a small ferrite transformer, and a microwave transformer core or any other reasonable sized core, and wind your own transformers.


Using this system, you can store the charge from the small multivibrator into a capacitor, and then discharge it into a decent core to develop  lots of watts for a small time period..... less then 10/millionth of a second or so....... its a bull stopper.

I have seen up to 400000 watts from this design.... it is simple and very cheap.


DONT US BARBED WIRE EVER!!!! with an electric fence...... getting caught /tangled on a hot barbed wire fence is deadly to some people with iffy hearts and can easily kill a cow in this instance.

No one uses high tension coils anymore, they are next to useless because of the tiny current they produce. Any fence load (grass etc) will knock it down very quickly. A low impedance solution burns the grass (kill not burn ) off the fence.

A 15ma solution will totally wipe out an igntion coil solution...... plus the unloaded voltage is illegal as it will be in the 20000v region... 10000 is the limit here and NewZealand.... I assume it is there too.



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

Offline madlabs

  • Full Member
  • ***
  • Posts: 113
  • Karma: +7/-0
    • Chief Bottle Washer
Re: Electric Fence Zapper
« Reply #7 on: November 30, 2012, 09:46:59 am »
Oz, Phil, All,

Turns out I musta done something wrong measuring the current draw of the circuit. It actually draws less than 1mA except for the LED blink. Tough to determine voltage from distance unless you have a proper spark gap with spheres. As to bears, luckily I live in northern CA where all we have is small black bears not known for attacking people. But they are known for climbing apple trees and destroying them.

The fence is quite short, only around 700 feet. I actually do have mains (inverter) power out there. Oz, I'm quite interested in your circuit and board. By any chance do you use Eagle? If not, even a jpeg would do. Or I can use your art to make an Eagle version. I have no problem doing some xfrmr winding. Out of curiousity, how many wraps of what gauge?

Thanks!

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 oztules

  • Forum Advisors
  • Hero Member
  • ****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Re: Electric Fence Zapper
« Reply #8 on: November 30, 2012, 02:04:25 pm »
Jonathan,
12vdc is fine, 240ac volts is fine, 110ac volts is not fine, and would need a little step up transformer to get to the higher voltages needed for storage..... a step up will use some extra magnetising current, but apart from that no change.

I use two boards, one for 12vdc, and another for 240vac. The ac one uses a simple voltage doubler/rectifier to get the 640 volts, the 12v uses single transistor with small ferrite to make the 600v+

When we store this in a capacitor, we can get the energy from 1/2 C (in farads)xV (volts)^2.. 1/2 capxvoltage squared.

We then use a simple diac discharge circuit into an scr/triac... so as the charge voltage rises, we use a sample to trigger the diac at say 600v, and this discharges all that energy into a core.

The tiny ferrite I use is an e49 core, with about two lots of 18 turns of 1mm wire for the primary. One winding for the feedback to make it silly simple, the other primary as the switched primary. The secondary can be 400 turns of spiderweb, as it is small current high voltage.

The power transformer I use are the microwave ones... free so cheap I suggest.

When you dump up to 60 joules into a core (even a 1kw core) it will saturate to hell, but it does not matter for this one shot system.

It consists of 9 turns 2 in hand 1.8mm to 2mm wire (about #12 or #13 AWG) for the primary, and about 200-260 turns for the secondary, I use 1mm wire for that.

The transformer can be just welded/epoxied back  together as it was originally for the microwave duty, don't need to do the I E thing.


The power transformer needs to be neatly  ( side by side wire) wound with each layer separated by motor/transformer paper. This will give us reasonable isolation between each layer and stop the enamel from trying to keep isolation between each layer, the paper does that. We need to leave 3/16th inch of paper over/past each winding layer for the same reason.

It's simple, easy, and very effective technique for very high voltage transformers...... then epoxy the transformer too keep moisture out and you have a very commercial grade fencer for a 5-20 dollars instead of a thousand dollars.

I will do an article for you if you wish. The circuit board is done with protel, never liked eagle.

Try to get picture or gif of unit and board today, maybe article in a few days.


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


A tiny 15ma fencer can use as little as a few uf capacitor into a small transformer for light fencing, and same circuit into a 100-200uf capacitor with a bigger core will get you up into the hundreds of thousands of watts, and draw over an amp..... this will light up a many many tens of miles fence, burn off the grass, andstill pull over 8000v @ 30 - 40 ampsinto a 300 ohm(heavy) fence...... same board and circuit etc.
Flinders Island...... Australia

Offline Wolvenar

  • Senior Moderator
  • Hero Member
  • *******
  • Posts: 1474
  • Karma: +40/-0
  • Mr. Murphys pawn
Re: Electric Fence Zapper
« Reply #9 on: November 30, 2012, 03:28:54 pm »
At a friends place I setup a store bought fencer on a bird feeder post in an attempt to scare off a repeat offender bear raiding it.
I set a pipe in concrete within a couple pvc pipe/concrete layers.

I don't remember the specs of this fencer but I do know it worked.
To set this up you have to know this fird feeder is on the edge of a retaining wall.
When I replaced the feeder I made it high enough that the feeder itself could not be reached by the bear on its hind legs.

When the bear came for his nightly raid he noticed he couldnt just reach the feeder.
He touched the pole with his paw and was rather surprised, recoiled looked around then decided to rear up on hind legs to push the pole down since he could not reach the feeder any more.

Well I wish I had it on video. He pushed into the pole got zapped then fell completely into it like he lost control of his balance, face first into the pole and off the side of the 4' retaining wall.

That bear got up and ran like hell away, never looking back.
He still sticks around the area but wont come even close to the house anymore.

I don't have a lot of images of this I guess but.
The inside pipe, the other 1' pvc was placed in cement in the ground and this placed in it, and more cement.


A shot of the retaining wall, but not a good one to show its height.
Before the new setup.


This had a feeder with a zapper to keep squirrels off.
The bear had taken this down earlier and broke a few perches.
I had to fix that as well as a few places squirrels chewed.
They took immediate advantage of the fact it was down and they could get to it in ways they wouldn't get zapped


So in this case a fencer deterred a good sized bear rather well.
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)

Offline oztules

  • Forum Advisors
  • Hero Member
  • ****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Re: Electric Fence Zapper
« Reply #10 on: November 30, 2012, 06:39:03 pm »
Here is a screen shot of the board to show how simple it can be, will do more on this for you later

1687-0

I like to fill in the board with as much copper as I can...... saves on ferric chloride :)

Here are both the 240v version and the 12v version





The capacitor (storage ) is external to the board, as the 50uf 600vac caps are rather large.
The smaller brown caps on the board are for wave shaping in conjunction with the inductor you can see.

The white capacitor on the 240v board is used for doubling and current limiting for when the scr's short the source and cap out direct to the big transformer ... also located remotely..


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

Offline madlabs

  • Full Member
  • ***
  • Posts: 113
  • Karma: +7/-0
    • Chief Bottle Washer
Re: Electric Fence Zapper
« Reply #11 on: December 01, 2012, 11:56:46 am »
Oz,

That looks perfect! I'll do the 12V version as I only have (and will only have) 120VAC in the orchard and already have the small solar panel and so on. The boards in the picture are well within my in house capabilities and I bet I have most of the components kicking around, I have lots of orange drop caps and so on. Do you have a BOM so I can poke around and see what I need? The oven xfrmr looks like the newer, smaller kind, which is good because they are easier to get. A quick trip to the dump will provide one. I have some large older ones but they have been modified for silly high voltage projects and I'd like to hang on to 'em for that.

Does Protel have a freeware version? I'll look into that. I'm not married to Eagle.

Thanks a ton for the help, I think this will be much better tahn my ignition coil model. Although now I'm going to have to find something entertaining to do with it since I made such a nice board and it does toss a nice hot spark. Now who or what can I zap with it... (starts thinking evil thoughts....)

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 oztules

  • Forum Advisors
  • Hero Member
  • ****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Re: Electric Fence Zapper
« Reply #12 on: December 01, 2012, 03:08:40 pm »
Sadly, thats not the oven transformer..... thats only the etd 49 step up transformer...
the oven transformer is heavy and as big or bigger than the board... yes a normal microwave tranny...Will get a pic of one converted for you today.

Circuits are not my thing, I make one up while drawing the board, then make a board, then modify the board a few times and throw away the circuit and make the changes from the prototype board .... just bad habits I guess.... the circuit original gets changed so much, it seems not worth remembering in most cases.

I will redo the board so that it is clear what the parts are.

You will note the 240v version does not have the step up, but still needs the power transformer for both current dumping, and galvanic isolation from the mains.

Yes the boards are simple, as is the entire circuit..

I will explain each part and what it does etc a little later today or tomorrow.

suffice to say    oscillator ( about 5 parts inc tranny) goes to rectifier (2 diodes) a damper circuit (resistor and another diode) to a big capacitor in my case (small in your case). About half a dozen parts in the voltage divider for the diac trigger (only because the voltage (600v) is high, so we need a few resistors in series to stop arcing ). Next is the triac bundle (much cheaper than 50 or 100 amp 1000v scr's), a ferrite ring and a few turns of wire, and two 2uf capacitors for wave form smoothing..... and thats it but for the power tranny.

For your purposes, a small power tranny will do, and probably only one or so triacs, and a small cap.

You will only ever get milliamps and spark from an ignition coil, you can gets tens of amps and thousands of volts from the low impedance version.... more power, just bigger caps and transformer..... down side is nothing is for nothing, if you want hundreds of thousands of output watts, it will cost some more current, bigger solar panel.... but  for what you want, you will bluff anything about the place for 10-20ma... good for 5 kms or more....bigger tranny and caps... then 75kms or more circuit remains nearly the same.

I found the ignition coils ones were only good for temporary  haystack protection, or  small temporary fences with no leakage (as they were temporary, and no time for grass to grow into them).... but for a real life fence, they are rubbish.... they just don't have the current to go on with their impressive open circuit sparks.



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

Edit:
A download for protel for windows is here:

http://webcache.googleusercontent.com/search?hl=en-AU&biw=&bih=&q=cache:x2gyaH8_c6sJ:http://www.pcb-pool.com/ppuk/service_downloads.html%2Bfree+download+protel+for+windows+1.5&gbv=2&gs_l=heirloom-hp.1.5.0i30l2j0i8j0i8i30l4.3951.14742.0.25130.35.34.1.0.0.0.1378.8480.9j12j5j3j1j3j0j1.34.0...0.0...1c.1.k69TSHudPxM&ct=clnk

It is a demo only, so won't save files, but other than that seems to work.
Use download #123, #124 near page bottom, and it should unzip and install. needs both "disks"/downloads.

PM me for more useful information/download on protel for windows ::) if you get my drift... re saving files etc.
Flinders Island...... Australia

Offline madlabs

  • Full Member
  • ***
  • Posts: 113
  • Karma: +7/-0
    • Chief Bottle Washer
Re: Electric Fence Zapper
« Reply #13 on: December 02, 2012, 11:49:32 am »
Drat. That version won't work with my version of windows, which is Vista. And Tuesday I get a new machine that will be running Win8. Oh well, Eagle aint too bad.

Looking forward to the schematic though. Thanks Oz.

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 Wolvenar

  • Senior Moderator
  • Hero Member
  • *******
  • Posts: 1474
  • Karma: +40/-0
  • Mr. Murphys pawn
Re: Electric Fence Zapper
« Reply #14 on: December 02, 2012, 12:25:16 pm »
Oh man.. feel sorry for ya, one bad OS to an even worse one.
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)