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I am building an electric fence driver and need to know if has too much or too little power

Discussion in 'Power Electronics' started by antrowe07, Feb 23, 2020.

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  1. antrowe07


    Aug 30, 2019
    So I'm not as much worried about the circuit as much as I am the size of the flyback transformer and mosfet,i am testing with an IRF640 and a small Canon flyback transformer from an old laser printer and it will produce arcs of about 3/4 of an inch. I'm using a pulsed power supply of 19v. I thought the pulsating was the circuit but when I change the power supply it stopped pulsating and it would make continuous arcs. I really just need to know if what I have will harm people or animals too much.. Thanks in advance 15824718578971206156583.jpg
  2. duke37


    Jan 9, 2011
    Electric fence drivers vary widely in the power of the shock. They are specified in terms of energy rather than volts or amps, A small fence would be adequatelt powered with 0.1J but a long fence in Australia may use 10J (but Australians are tough). The energy is normally provided from a high voltage capacitor which is charged to the correct voltage (300V) and discharged through a transformer (about 1:20) You must leave a blank time between pulses for the victim to withdraw before the next pulse. Normally the pulses are spaced at one/second. In the UK a notice must be displayed tp warn little chilldren and other animals.

    The voltage must be high enough to punch through hair or fur. A long fence will have a considerable capacitance which needs to charged at each pulse

    Your circuit shows a rectangular box, I assume this is a 555 which produces continuous pulses. I have not worked out the frequency. If your transformer can store 0.1J then your circuit could be used with the FET pulsed at one second intervals. There is nothing to control the FET current which could be excessive if the output is shorted.
  3. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Your electric fence definitely needs to be pulsed with a sufficient interval between pulses to allow whatever is being shocked to disengage from the fence. If excited continuously, lethal results could occur. Only Government entities are allowed to use lethal force in this manner.
  4. Nanren888


    Nov 8, 2015
    In some places electric fences in urban areas are banned. I guess you;re not in an urban area.
    Fences for cows might be quite different, or set differentlt, from those for smaller animals.
    Discharging from a capacitor is a good concept as you can calculate the maximum energy delivered.
    A monster 58 Joules.

    100 Joules

    As a guide, commercial units will cause removal of teeth, if the victim gets the pulse right.
    Farms often need big ones are weeds grow up into contact with the wire & sap some of the pulse energy down the fenceline.
  5. antrowe07


    Aug 30, 2019
  6. antrowe07


    Aug 30, 2019
    I messed up in the first thread,what I meant to say was with the 19v power supply for some reason it was pulsating but when I changed supplies it ran a continuous arc with no pulse,i plan to look around for an actual fence driver circuit as I was hoping to use the 555 flyback circuit I posted,,I already have a store bought 2 mile charger and just need something bigger,like I said I think I'll look for a different circuit just to be on the same side..thank you for your time and response
  7. antrowe07


    Aug 30, 2019
    Thank u for your time and response,with the information i now have I believe I'll just go look for an electric fence driver circuit instead of the flyback circuit I intended to use,i planned to add a cap if needed and I misspoke when I asked,,it actually had a pulsed output but only while using a certain power supply. I figured out the power supply was bad and using a different supply gave me continuous be safe I will look for a different circuit and a transformer that isn't a flyback,,once again thank you very much
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