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Discussion in 'Electronic Design' started by Dirk Bruere at Neopax, Sep 12, 2005.

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  1. Another tricky problem in brain electrocution:)

    I want to do some experiments on the effects of HV VLF electric fields on the
    brain. The frequencies involved are 4Hz upwards and I'd like to use a sine
    rather than spike waveform. Voltages to be approx 3000V/m upwards (values found
    during thunderstorms).

    The tentative setup would be to feed the AC signal to two large insulated
    conductive plates, probably around 500mm x 500mm with a separation of at least
    300mm, probably quite a bit more. The head would placed between them.

    Now, transformers are not esp efficient at 4Hz, but then again I do not need to
    drive much current (I think). Can anyone suggest what the transformer would look
    like eg turns, core etc? Suggestions for driving circuit also welcome.


    The Consensus:-
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  2. Tim Wescott

    Tim Wescott Guest

    Not _my_ head!

    At that low of frequency, and at the (implied) low current I would be
    thinking of driving the plates with active devices. I suspect that
    there are IGBT's that will do the job, and if not I have some VT-4C's in
    my attic that should be able to stand 3kV on their plates.

    Please note that I will have _nothing_ to do with this if you kill
    somebody. Safety is your responsibility, not mine. If you sue me do it
    in Kansas*. All of the safety measures that are implied by sticking
    someone's head between a couple of plates carrying 1kV between them
    should be observed (or even sticking a dog's or sheep's head in there
    whilst and at the same time holding onto the animal). In fact, find a
    few extra safety measures and stick to them, too.

    - - - -

    * My sister lived there for a while. While many of their cultural norms
    make this agnostic, non-conformist west-coaster gag they do have the
    refreshing opinion that if you do something stupid with someone else's
    property it's your mistake to pay for, not McDonald's or my insurance
  3. Well, I want sub mA current flow on short circuit, so it shouldn't be too
    dangerous. I suspect your method might lead to instant lobotomy at best in case
    of accident.

    I suppose I'll have to work out the ballpark capacitance and stuff...


    The Consensus:-
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  4. How do you propose exposing the brain to the electrostatic field? The
    skull and tissues of the scalp will be a pretty good electrostatic
    screen at those frequencies.
  5. Tim Wescott

    Tim Wescott Guest

    Resistor-coupled amplifiers, with high resistance will give you
    automatic current limiting:

    | | R = BIG
    | |
    ------------| (or some other amplifying device)
    created by Andy´s ASCII-Circuit v1.24.140803 Beta

    But I'd be concerned about capacitances, also.
  6. Probably.
    However, they will not be perfect.
    I'm interested because I have not seen anything documented on the effects of HV
    fields, or lack of effects.

    I assume that there will still be a polarising effect that extends through the
    head. Apparently even a few hundred mV applied directly can cause quite
    noticeable effects.


    The Consensus:-
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  7. Fred Bartoli

    Fred Bartoli Guest

    There can't be E field inside a conductor. Well at low frequency, and 4Hz
    is... low.
  8. Depends how good the conductor is.
    Anyone tried it?
    I would also have thought that it might induce current flow by capacitative


    The Consensus:-
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  9. Fred Bartoli

    Fred Bartoli Guest

    Get some sense of reality:

    How much is the intrinsic capacitance of 0.2m diameter sphere?
    How much is the resistivity of human tissues.
    Evaluate the time constant.
    Then you can have an idea of the voltage gradient wrt to your frequency.

    But I know in my bones, err... preferably in yours, that it'll be almost

    But then, if you do want to induce some real E field, why don't you put the
    electrodes directly in contact?

    I guess Joerg can give you some advice on building a debrainillator...
  10. Well, as part of the expt I will also be trying VLF modulation of kHz fields.
    Because I know about that technology already.
    Armchair theorists say all kinds of things are not possible, until some
    experiment shows they are. Then it's a case of "...of course it will work if XXX
    is taken into account". An ounce of experiment is worth a tonne of theory.
    google, electrosleep
    12000 hits


    The Consensus:-
    The political party for the new millenium
  11. Dirk Bruere at Neopax wrote...
    If you don't think it's too dangerous, that's a very bad sign.

    You mention 3kV/m with 0.3m plate spacings, which works out to 900V.
    My latest HV amplifier design does +/-1200V, which would meet those
    specs, but I think I'll not give you the details! Ahem. Here's a
    +/-4kV amplifier on eBay ... However I recommend against it in your
  12. Well, we have Fred saying how there will be no effect whatsoever, and you
    implying that it's a suicide machine.
    Care to elaborate? Bear in mind that electrosleep machines have a very long and
    safe history when it comes to actually passing sub mA current through the head.

    You think the electric field alone will be more dangerous?

    And I *do* know how to build amplifiers that will pump out kV and kW - it's just
    that I don't actually want high power and complexity. Hence the transformer


    The Consensus:-
    The political party for the new millenium
  13. Dirk Bruere at Neopax wrote...
    If the electrodes are exposed, they're dangerous to the touch.
    You don't believe that? If the electrodes aren't exposed, on
    account of insulation, most of the electric field ends up being
    developed across the insulator, and not across the conducting
    subject matter, the head and brain.

    If you want to induce 500uA electrosleep currents in the head,
    use electrodes: "The electrodes may be saline-gauze sponges over
    metal plates applied between frontal and occipital locations."

    There's also the electrosleep band. "Musically electrosleep assault
    and dazzle the listener with dueling guitars, cascading keyboards
    and manic vocals." No electrodes needed... Here's a sample:

    Also, I found this: "I would advise against making your own machine
    unless you are a very good electrical engineer with a good bio-medical
    background. Good luck in finding a doctor who won't laugh his narrow-
    minded, prejudiced, priest-like ass off when you mention this."
  14. Not if they are powered at 900V with a short circuit current not exceeding 1mA
    That's why I don't think your amp is of much use to me.
    And it is why I asked a question about transformers at VLF. Certainly not
    efficient, but I don't want efficiency. The voltage is only going to insulated
    electrodes with a capacitance in the pF so the current should be negligible at
    sub 10Hz frequencies.
    And it will *probably* have no effect, but it's worth trying as part of the
    expt. The other part of the expt involves modulating a kHz kV waveform with VLF.
    No, been there, done that.
    Actually, I do have a doctor friend who doesn't laugh at such things.
    However, this has nothing whatsoever to do with medicine.


    The Consensus:-
    The political party for the new millenium
  15. Maybe start with something like one of these:

    Good Luck!

    (Of course, if you really want to trigger a person's brain into action,
    just find their hotbuttons and prod them until you piss them off. >:-> )
  16. Rich Grise

    Rich Grise Guest

    So, he wants cooked brains?

    Good Luck!
  17. Rich Grise

    Rich Grise Guest

    Well, I got a very respectable jolt once from a car coil that I had hooked
    to a toy train transformer: 19 VAC, 60 HZ to the primary, and making fun
    arcs with what came from the secondary, until I got my thumbs on opposite
    terminals. BZZZZAAAAAAAT!!!

    Of course, that had nothing to do with my current mental condition, nope,
    no brain damage at all, not a bit, nope, nope, nope, nope.....

  18. Rich Grise

    Rich Grise Guest

  19. Rich Grise

    Rich Grise Guest

    FOUR HERTZ!!?!?!? I first read Dirk's post as "4 KHz".

    Heck, just get a big rubber balloon, rub it in your hair, and wave
    it around!

    Good Luck!
  20. Chris Jones

    Chris Jones Guest

    If he is actually wanting the high electric field inside his flesh, then
    obviously there will be a problem. Providing he is investigating the
    effect of the head being placed in a volume of air which has an electric
    field in it, then he should be fine. I think it would be possible (but
    tedious) to do this in a way that meets all appliance safety regulations.
    (e.g. TV sets can cause high electric fields in front of the glass.) I
    thing that if the plates are insulated behind 6mm of polypropylene (or
    whatever thickness one is legally supposed to use for the voltage in
    question), then the electric field in the gap between the plates will
    hardly be affected by the insulation, (at least for AC fields). Since the
    dielectric constant of the insulating sheets will be greater than that of
    air, the insulating sheets will drop less AC voltage than the same
    thickness of air would.

    Actually this idea of applying high voltage AC fields to the head sounds a
    bit like the electrostatic headphones I built, adapted from from some in a
    '70s Wireless World magazine. I think I had about 500Vp-p (1kVp-p
    differential) of audio on each set of perforated plates (which were just
    100mm square plates of single sided FR4 with lots of 3mm holes, and etched
    sections around the edge), with a piece of kitchen cling-film stretched
    over spacers in between the plates, the cling-film was charged to about 1kV
    DC, through a resistor of a few tens of Megs made out of many resistors in
    series so that several could fail quite safely. I connected several high
    voltage ceramic capacitors in series with each amplifier output (each one
    rated for more than the supply voltage), with a DC bias resistor from the
    headphone connector to ground. The amplifier output stages were common
    emitter with resistive loads so the resistors would stop it from killing me
    anyway even if all of the many series connected caps were to fail. The AC
    signal current from the amplifier was not dangerous, it just tickled if you
    touched it, since it could only provide enough current to drive the couple
    of hundred pF of the headphones.

    The headphones sounded really good. With the voltage of my amplifier they
    weren't quite loud enough, and had a tendency to collect dust inside, so
    they needed frequent disassembly and cleaning.

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