need help for developing an electric fencing for my farm

:?

SIR,
MYSELF IS HRISHIKESH WAGH ,WORKING TO MAKE A ELECTRIC FENCING CIRCUIT ,FOR PROTECTING MY FARM FROM WILD ANIMALS
.I WANT TO DESIGN A SWITCHING DEVICE WHICH WILL REMAIN ON FOR
1MS AND REMAIN CLOSE FOR 1.2 SECOND.

* CAN U GIVE ME THE IDEA ABOUT WHAT SHOULD BE THE AMT OF CURRENT & VOLTAGE FLOW THROUGH IT.

HRISHIKESH WAGH

Hi Hrishikesh,
I made up an electric fence kit that works on 12 volts and only draws 190milliamps. I bought the kit from dick Smiths but it's a discontinued kit so it isn't avalaible but here is a schematic of the circuit.


Cheers Bryan1

Fence charger

How about a hill billy fence charger. I saw one that a guy was using once that was an ignition coil from a car. He had it powered off a car battery and the wire that is supposed to go to the distributor- he had hooked to his fence. I thought that it would be a good idea if it was powered from a dc power supply and incorporated a simple timing circuit. There are several schematics for fence charger circuits in the "Encyclopedia of Electronic Circuits".

conserning voltage: I have a commercial fencer that puts out 10,000 volts no load, with a few miles of fence, especially if there is grass on it the voltage drops to 4,000.

Also a word of caution, one time a while ago a 3 month old baby goat got caught in it....it was killed in about 4 minutes as close as I can tell. I contacted the company, and they said it can kill animals under 50 lbs. if they get caught and cannot get away.

Also I know a story of someone who made a fencer, and a child got caught in it...sad story

goodpickles said:

Also a word of caution, one time a while ago a 3 month old baby goat got caught in it....it was killed in about 4 minutes as close as I can tell. I contacted the company, and they said it can kill animals under 50 lbs. if they get caught and cannot get away.

Also I know a story of someone who made a fencer, and a child got caught in it...sad story

Click to expand...

Perhaps the controller circuit could be modified to detect a load (such as animal or child), and automatically cut off the power for 1 minute, say, 20 seconds after detecting the load.

This would surely help prevent such tragedies.

It would be helpful if it could be made to work...I have I think it would cutoff as soon as a little grass is on the fence...and I don't relish weedeatering my fence I have about a mile :wink:

With a Current detection Circuit and a 555 timer, it could be easily made to Cut Off after X Number of Seconds.
The Problem would be to have it Automatically turn back on after that Load is Removed.

Without that you may never know if your fence is protected or not.

I'm glad somebody mentioned the part about something or someone getting hurt. I thought about that last night after making the "homemade suggestion". Thanks

I think that the usual way of obtaining the high voltages for electric fences is to use an inductor (or a coil) when you pass current through the inductor energy is stored in the magnetic field of the inductor. You then stop the current flowing into the inductor by breaking a switch. The inductor will attempt to keep the current flowing through it which causes the voltage across the inductor to rise very rapidly and to a very high voltage. This system can be made to work from a 12V battery and capable of making voltages in te kV range.

Like others have already said making electric fence devices is dangerous - if you don't really know what you are doing then you could easily make something that will be harmful to humans.

I think these slots into the same grove... I'd like to build a Stun gun that works like an electric fence... by only touching one contact point the attacker must get the living hell shocked out of him...

On another note I’m thinking of electrifying a safe with a CAP to prevent contentious shock

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The most important thing in the world is protecting your family.

How do you plan to touch the safe to open it then? It's a bit pointless if you don't electrify the keypad.

I'm pretty sure I saw a fence electrifier at Princess Auto (surplus place) for $50. Why build one?

Build a remote power switch. if you've got a 400 voltcap and you only touch the one contact will you get a shock??

Get a coil out of an old car this will produce about 10,000 Volts from a 12Volt battery. You will have to switch the primary,the lead that goes to the side of the distributor is the primary. A small D.C. motor can open and close the contacts. Connect the plug side of the coil to your wire fence.

The ones I know about are designed like a stun gun; they are high voltage pulses with very limited current capacity. This can cause pain but is very unlikely to cause death. IMHO it would be wise to avoid ignition coils, high voltage capacitors, etc. Those things will probably set the grass on fire too. In fact I'd advise going with a safe commercial product and forgetting the homebrew idea altogether.

Are there any designs for sall units to attach to a bird feeder to shock or kill squirrels thatdestroy the bird feeders

Now that would have to be one intelligent ciruit I think. An electric shocker that can distinguish between a squirrel and a bird. It would be pointless attaching a shocker to the bird feeder otherwise, You'll kill the poor birdies aswell as the squirrels.

Paul...

There are low energy and high energy units; the high energy units will set grass on fire.

Electric fence

Hi Hrishilkesh,

I read all the posts and the danger involved using an electric fence. If you just want to keep animals out of the fenced in area I assume that they are able to climb the fence. To electrify the top the fence won't hurt birds. They have to touch the HV-wire and earth simultaneously which is kind of impossible with their short legs.

Here is a circuit which is also used for cow fencing in Germany.

It consists basically of a timer circuit activating an ordinary ignition coil at regular intervals. The shock power can be set to three different levels starting at 250mJ up to 450mJ.

The circuit uses a CMOS-version of the NE555 timer, because of the relatively high capacitance an NE555 would have to have for the same timing.

The ignition coil should ideally be one used for electronic ignition circuits with a resistance of 0.7Ω.

To ensure proper function at all times the circuit uses a dual switch to select pulse timing. If the circuit fails and the timer output stays high the switching transistor and/or the ignition coil will fry. Therefor the fuse is mandatory.

If the circuit is made properly it should put out pulses of 20 to 25KV, high enough to keep the animals off the fence.

Hans

Actually, kendallroad and hackableFM, the difference between squirrel and bird locomotion makes it practical, albeit not perfect, to target one or the other with an electric barrier by placement. Assuming the feeder to be pole-mounted (as opposed to suspended), locating the electric barrier on the pole, not the feeder platform, should achieve near perfect targeting. If the feeder is suspended, place the electric barrier on the arm supporting the feeder and/or use a smooth wire instead of a chain for suspension. You might even insulate the smooth suspension wire at both ends, energize it, and ground the suspension arm. Of course, you have to consider the excellent acrobatic jumping capabilities of squirrels.

I found this thread by searching for a solution for my own squirrel and bird problem, which is how to keep both of them out of my raised bed strawberry and vegetable crops. The squirrels cleared out the entire strawberry crop just as it was approaching perfection for shortcake. Screen can work, but make it too much of a bother to tend to and pick the crop.

I don't have a solution yet, but have been scheming about a very simple, low-power circuit to inject a string of low energy pulse into a grid of wires strung across the crop a few inches above the soil level. Not perfect coverage, by far, but perhaps enough to develop an aversion reaction in the crop robbers.

I'm still groping for info on appropriate energy/voltage levels that would be completely safe, but discourage the robbers. I am concerned that devices using auto ignition coils fed with 12 volts might be a bit too powerful for my intended targets. I also don't want a dead animal disposal problem in my urban setting and I don't want terrified grandchildren and angry parents. I regard this as a contest between me and the robbers that requires finesse, not a blood feud. Perhaps a motorcycle ignition coil or a flyback transformer fed with less than 12 volts and with an energy-limiting capacitor feeding the primary? Hans' German circuit looks like a good start. I'm a little worried about how to test the tolerability of the results by humans, how many tests would be required, and how to recruit testers, but I'll cross that bridge when I get to it.

By the way, kendallroad, if you google "electric squirrel fence" or the like you will find line, battery, or solar powered commercial units in the US$50 to $100 range for garden use targeted at small animals. I just hate to buy something I can make, but liability is a consideration. I assume that Hrishilkesh has already googled, "electric fence" and read the info on the websites of the many commercial unit manufacturers.

Be safe and have fun.

awright

Pondering the schematic posted by Hans, I realize (I think) that this circuit uses the ignition coil in flyback mode, as it is traditionally used in an auto, not as a transformer of an input pulse. That is, prior to the pulse, the primary circuit is completed from the 12V bus through the primary to ground via the MOSFET, thus magnetizing the core. The HV pulse is then generated when the primary current is interrupted by the MOSFET turning off. The significance of this is that the energy of the pulse cannot be controlled by varying the size of the capacitor feeding the primary, since the energy is fixed by the degree of magnetization of the core at the instant the "points" open, not in the capacitor feeding the primary. Pulse energy level can, however, be controlled by varying the voltage (and, therefore, the steady-state current) in the primary prior to opening of the primary circuit.

I think there are efficiency losses in this type of circuit because the primary current will flow longer than is actually required to magnetize the core while waiting for the opening of the "points." Perhaps one of the newer SMPS ICs that detect primary current as it builds up to an adjustable value could be beneficially used here. Hmmmm. Pulse repetition rate could be controlled by supply voltage and energy level controlled by current sense.

Not actually claiming intimate knowledge of ignition or SMPS circuits.

awright