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Electric fences

Discussion in 'Electronic Design' started by Alan Beamish, Aug 23, 2007.

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  1. Alan Beamish

    Alan Beamish Guest

    I'm about to get some chickens and was thinking that an electric fence might
    help to deter foxes. Does anybody know how the fence energisers work ? I
    thought I might try experimenting with an old ignition coil and relay to
    open and close the primary coil but I imagine that the primary current would
    be high. Any thoughts will be gratefully received.

    Thanks,

    Alan
     
  2. Ecnerwal

    Ecnerwal Guest

    Buy one. Roll-your-own electric fence chargers are a liability lawyer's
    wet dream.

    Meanwhile, the foxes will just burrow under it and not be bothered a
    bit. If your chickens are not shut up tight at night, they are going to
    be eaten - so I'd suggest you put the effort into a nice tight coop, and
    remembering to shut it every night (and open it every morning).
     
  3. Hugh Fearnley-Whittingstall is an advocate of the ladder system. The
    hen house is raised on an old telegraph pole, or similar stout
    support, to a height of about two metres. Access to the hen house is
    via a ladder, made by knocking simple steps into a long, stout pole.
    The design of the ladder is deliberately crude and rickety: a chicken
    will be able to use it, but a fox will not.


    Martin
     
  4. One could make such a ladder from a pole mounted in a bearing at either
    end and balanced so that the weight of a chicken will not cause it to
    rotate but that of a fox will. If a fox tries to climb it, it just rolls
    180°.
     
  5. see if you can download some of his programs. Somewhat British, and
    funny
    And his teeth seem OK (generic brit joke)


    Martin
     
  6. Barry Lennox

    Barry Lennox Guest

    You could have a metal patch on every second ladder step connected to
    an energiser. Chickens would use every step and not notice it, foxes
    being much longer, would use every second or more step and take a
    shock across their legs.

    "Silicon Chip" has had at least three designs Apr 99, Jul 95 and Apr
    93. Back issues can be got from http://www.siliconchip.com.au/

    HTH.

    Barry
     
  7. HapticZ

    HapticZ Guest

    2 meters,six feet, is a piece of cake for any wild animal to jump up to!

    breed enough extra sacrifice chicks to size, then allow fox to cull them and
    reduce your prize stock loss to a minimum.

    buy a dog that likes chickens. get some geese also, to use as watch geese
     
  8. HapticZ

    HapticZ Guest

    a weight sensitive switch connected to a shotgun or taser!

    or a door that closes to prevent escape if fox does get in, then you can
    dispach it immediately

    a double entry arrangement, with tight turns too close for fox to negotiate.
     
  9. Rich Grise

    Rich Grise Guest

    I'm having a hexx of a time trying to visualize something that a chicken
    can climb, but a fox can't.

    Is there anything like a picture of one anywhere? Or better yet, a video
    of one in action?

    And, how do the chickens know they're _supposed to_ climb this thing? ?:-/

    Thanks,
    Rich
     
  10. Rich Grise

    Rich Grise Guest

    Concertina Wire. >:->

    Cheers!
    Rich
     
  11. John B

    John B Guest

    Everything you need is here, including a ready-made PCB.


    http://www.elektor.com/magazines/2006/may/electric-fence-energiser.58236
    ..lynkx
     
  12. AndyS

    AndyS Guest

    Andy writes:
    I built on many years ago with a old Volkswagon ignition coil.

    I used a 555 timer which put out a pulse about twice a second. This
    pulse drove a IRF620 hexfet which could switch 10 amps or so. The
    width of the pulse was experimentally determined to allow the
    coil current to build up to about 5 amps. The average current from
    the battery (12 V) was about 5 milliamperes.

    I experimented with using the electric fence with goats, turkeys,
    and
    a cat........

    Goats figure it out, and the first one to learn to go over/under
    the fence
    will show all the others.

    Turkeys are just too dumb to care... I think they like it...

    The cat sensed the electric field, jumped up on a post, and peed on
    me...

    I suspect that a fox is smarter than a goat......

    So, you can make your own fence charger cheaply, as I have done,
    but it may not accomplish what you want.... Good luck...

    Andy W4OAH
     
  13. Gary Tait

    Gary Tait Guest

    They work by charging a capacitor (from AC mains current or a battery
    through a step up trasnformer driven by an oscillator, kind of like a
    heavy duty camera flash or strobe light), then discharging it through a
    step up trasnformer. They typically use a BJT transistor oscillator to
    trigger an SCR to dump the capacitor to the step up trasnformer, which
    is typically custom made. They usually output 1-6 KV per pulse, peak I
    guess. I have a special voltmeter for measuring that sort of fence, and
    thats what it reads.

    Look up Gallagher fence chargers, they will have all sorts of info on
    them.
     
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