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8000 Volts — Parallax Forums

8000 Volts

jamachinejamachine Posts: 3
edited 2004-10-08 18:40 in BASIC Stamp
Anybody have a Idea on how to get this down to a reasonable voltage to monitor.I will explain alittle closer,what I want to do is to monitor a electric fence and use a bar graph or a row of LED'S to display a voltage level so I know if·the fence·is working or not,any Ideas????


Thanks Stan

Comments

  • Gerry ShandGerry Shand Posts: 45
    edited 2004-10-08 12:09
    Hi Stan:

    You can try one of two approaches:

    a. If the output waveform has enough AC in it, you can use a transformer to step the voltage down to a lower level, then rectify and filter to get a variable DC voltage as a function of AC voltage.

    b. Use a high impedance voltage divider network, then rectify and run into an opto-isolator. The opto can then provide a logic 0 or 1 into the stamp. There are some HV isolators out there from the likes of Burr Brown but they can cost a small fortune.

    Two important considerations:

    1. Safety, safety, safety. I am in an agricultural area and it is surprising how many people get shocked (Jeff Foxworthy jokes). So insure that the signal has been isolated and fusing is a must.
    2. You will be measuring from the fence wire to ground. Make sure that your input impedance is very high so as not to affect the operation of the unit. If you can open up the unit, you may be able to find some isolation circuitry inside that may provide a feedback signal to the switcher (if the electronics are that sophisticated) and you may be able to tie an input into the stamp this way. Keep in mind that once this is done, you have effectively voided the unit's warranty and affected its UL/NRTL rating which can have an impact on your insurance. Please be careful.

    Gerry
  • K de JongK de Jong Posts: 154
    edited 2004-10-08 12:26
    Hi Gary and Stan,

    Normally the current in these electric fence sytems is verry verry low but the voltage is high. So if you really take out current with a transformer or a valtage devider your system possibly will stop working.

    You could try a solution that works also with automotive ignition sytems. Take a piece of insulated wire and wind ond end two or three times around your fence wire. You then will be able to show the working of the electric fence by connecting one end of a small Neon light bulb (used in testing screwdriver i.e.) The other en will have to be put to ground and you will see the pusles on your fence.

    From that point you should be able to design a high impedance circuit which can connect to a Stamp. Make sure the signal for the stamp is limited to 5 Volts !!

    Remember, you are you are electrically isolated from the fence here and energy is comming from the three windings of insulated wire (induction) !!

    Succes,

    Klaus
  • Lee HarkerLee Harker Posts: 104
    edited 2004-10-08 14:00
    Stan,
    I don't mean to ruin your fun but you can get a fence tester at any farm store for a couple bucks. It is just a neon bulb with a large value resistor in series. One end is stuck in the ground and the other is clipped over the fence. There may not be much value in a bar graph of the voltage because it doesn't change. When I was a kid, I had to go around the fence line about once a month and pull out weeds that were touching the fence because they would short it out.
    It wasn't till I was a bit more knowledgeable about electricity that I realized why my little brother could touch the fence and not get shocked and I would. He was short enough that he had to stand on the bottom board of the wooden fence to reach the electric wire.
    Lee
  • jamachinejamachine Posts: 3
    edited 2004-10-08 18:40
    WOW !!!!

    Thanks for all of the Ideas, on the fence tester they are all to dim to see on a bright day and I have a horse that tests the fence all the time,he puts his nose up close to the wire and my guess is it makes the hair stand up on the end of his nose so he knows that is off.So what I need is something really visable and loud,now Klaus I think you helped me stumble into something I already have and that would be a inductive pickup for a old timing light.So I will go home and test it tonight to see if it changes·when the·voltage goes up or down,at 3000 volts he will go through it at 8000 VOLTS HE BUCKS,FARTS AND JUMPS.Yes I do get some satisfaction when it goes down he will keep going through it so I unplug it go fix the problem and wait for him to back through and plug a extension cord in to it and juice him, makes me feel better!!!



    Thanks Stan
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