How electric Fense work

Discussion in 'Embedded Systems and Microcontrollers' started by embpic, Oct 2, 2013.

  1. embpic

    Thread Starter Member

    May 29, 2013
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    Hello sir
    how does electric fense work with low voltage?
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    It uses a circuit to step up the voltage.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Usually High voltage pulses and Earth ground return.
    Max.
     
  4. Art

    Distinguished Member

    Sep 10, 2007
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    There was a kit in my country (Aus), that I built that used a vehicle's ignition coil.
    The kit didn't provide the coil, you were expected to go get one from the wreckers.
    It did the same thing the vehicle did to arc the spark plugs (low power unit).

    It used a 555 timer, and a resistor to delay sensing the primary was charged,
    so the primary was charged and interrupted in a cyclic fashion.

    I don't still have the fence controller, but I still have the circuit:
    [​IMG]

    but despite driving a fancy blue neon (that's neon, not LED),
    it will still only distress a Human a little less than those joke games
    sold in electronics gadget shops (this was neon light for PC case).
     
    Last edited: Oct 2, 2013
  5. sheldons

    Active Member

    Oct 26, 2011
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    post schematic
     
  6. #12

    Expert

    Nov 30, 2010
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    Fifty years ago I saw a fence charger that used a motor with a cam wheel that clicked a switch. The switch fired a car ignition coil, just like a car distributor would. Dead simple! No transistors at all in that design.
     
  7. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I started a thread some time ago about building my own fence charger, but some thought the topic was too dangerous, or sinister, or sadistic, or something, and should be banned, so I let it drop.
     
  8. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    This past spring as part of the Sandy Storm recovery I had to replace the bird wire driver on the Huntington Lighthouse. Without a charged wire birds roost all over the upper decks and make a mess. As it is, the seagulls tend to keep to the dock and just make messed there. Those can be swept off into the bay.

    We use a device from FiShock that sits in the sun and charges it's own internal battery. Very convenient for an installation where there is no electricity (like the middle of the bay where our light is).

    It puts out about a 5,000 volt pulse every second or so. I would not want the trouble to build something, especially when I need it to run for months at a time without any servicing.
     
  9. Art

    Distinguished Member

    Sep 10, 2007
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    Pretty much same here... Don't want to go any further unless someone actually makes a fence controller.

    The schematic is also copyright (came out of a magazine).
     
  10. Art

    Distinguished Member

    Sep 10, 2007
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    Thinking about it, a micro does sound ideal.
    You want to be able to vary both the on and off time of the pulse.
    If the on time is too long, you waste energy charging the coil,
    and also heat up your transistors.
    If the on time is too short, the field you want to collapse is potentially not established yet.

    Then it would appear the off time on the pulse would be an arbitrary setting for
    practicality of the fence.
    It occurs to me length of the off time will only determine the frequency of the same zap.
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Not so to me. An oscillator with individually adjustable on and off pulse times (which I don't think are necessary) can be made simply and cheaply using a single CMOS Schmitt inverter, 1 cap, 2 trimmer resistors, 2 diodes. For fixed on/off times lose the trimmers and one diode.
     
  12. embpic

    Thread Starter Member

    May 29, 2013
    187
    3
    any one have circuit diagram for that?
     
  13. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Here you go. Gives pulses of width ~100mS at ~1Hz with the components shown.
     
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