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Electrostatic precipitator from a bug zapper?

Discussion in 'Electronic Design' started by Adam, Jan 10, 2005.

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  1. Adam

    Adam Guest

    Hi. I would like to build an electrostatic precipitator. I have a bug
    zapper, and was wondering if I could just hook the leads from that to 2
    large plates, and put that in front of some grounded collector plates
    and a fan. I can't tell what voltage the bug zapper is using, but in
    general, do bug zappers put out enough to ionize the dust coming
    through? Its a zapper 40W bulb model btw, if anyone knows how much
    voltage it creates.

    Also, the mesh of the zapper gave me an idea-could I just straighten
    out the 2 screens, and flow the air perpendicular to them? Or would
    the dust lose its charge after passing the second plates?
    Any advice or suggestions are appreciated.

  2. Mark Jones

    Mark Jones Guest

    Hi Adam. A typical bug zapper probably puts out between 5 and 15kV. A
    typical air ionizer works at around 7.5kV, so at first glance this
    looks possible. But, there are gotchas:

    In electrostatic air precipitation, you want DC voltage, not AC. So
    on the outputs of your zapper, you'll need two 15kV-rated diodes. Once
    you have a high DC voltage, you want the negative lead to be the
    "emitter" and the positive lead to be the "collector." Electrons flow
    from the negative to positive terminals so this is why it's not the
    other way around. The emitter should be a fine wire - the smaller the
    diameter and longer, the more readily ions will jump off it and into
    the air. Take a long length of this wire and form a "grid" out of it.
    This puts "negative ions" into the air. (Be careful not to zap
    yourself, DC is very dangerous.)

    As for the collector, you want a large surface area with no little to
    no sharp points - the opposite of the emitter. Rounded sheets of metal
    work well, like an oval shape. Flat metal sheet might work also, as
    will a (fine mesh) screen. A course-mesh screen would probably not
    work all that well.

    Ions in the air are negatively charged. Most of these are strongly
    attracted to the positive plate and "dissappear." Sometimes the
    negative ions intercept a conaminant, and change its charge state. The
    positive plate is still strong enough to attract this ion, and thus
    the contaminant also. The end result is the positive plates get
    covered with gunk from the air.

    Let us know how it turns out.
  3. Adam

    Adam Guest

    Mark, thank you. I really appreciate your help. I went to home depot
    today and got the metal wires and sheets, but now I realize I have no
    idea which lead is positive and which is negative. I took the housing
    apart, and the transformer has no markings indicating anything, and
    both output leads are red. Is there any way I can test it to determine
    which lead is which?

    Thanks again,
  4. Robert Baer

    Robert Baer Guest

    Like the man said, it is AC.
    Gots to git some HV diodes...and maybe a HV cap for filtering..
  5. Mark Jones

    Mark Jones Guest

  6. Don Taylor

    Don Taylor Guest

    I had an odd thought. Any ideas about building an electrostatic
    precipitator that would fit somewhere between the manifold and
    the exhaust pipe of an automobile? I've seen some cars burning
    enough oil to be visible and I was wondering if there might be a
    way to cut that down substantially, and at a fraction of the cost
    of tearing the engine down and replacing all the rings, turning
    large volumes of air pollution into smaller volumes of solid waste

    Even a demonstration of feasibility would be interesting to try.
    But building something that can stand up to the abusive environment
    of the underside of a car seems like a daunting challenge.


    For those in the U.S. who might recognize it, maybe the...
    Ronco muffler cleaner :) For those of you who do not recognize
    this, Ronco is a company in the U.S. that sells some of the more
    questionable inventions to consumers.
  7. Robert Baer

    Robert Baer Guest

    If the rings or pistons are so bad that lotza oil gets but=rned, then
    *hiding* the result is really not the way to "solve" a problem.
    One should fix the (literally) stinking engine!
  8. Mark Jones

    Mark Jones Guest

    True. A mesh filter the diameter of a tailpipe would clog very
    quickly... how do you clean oil from a wire mesh filter? Hmmm.

    -- "Over-unity, UFO's, Zero-Point Energy... there's a reason
    scientists go 'mad.'" MCJ 200305
  9. Don Taylor

    Don Taylor Guest

    Well, to take one position, all the current emission control hardware
    and computer controlled compensation built into the recent cars seems
    like it isn't all that wildly different from what I'm suggesting here.
    I'm told an engine can be pretty far down the hill before the software
    just can't compensate for it anymore and you discover the problem.

    On the other hand, the adjacent state has high license fees, based on
    the value of the car. I think I see a larger number of old beaters
    over the border.

    It is easy to say what somebody else should do. But how many of those
    folks are going to pay a price equal to the majority of the current
    value of a car to get someone to tear an engine down to the ground
    and rebuild it? I question how much of car repair is cost justified.

    I know someone who sank $1200 into getting her transmission worked
    on, when to be really brutally honest, the car probably wouldn't sell
    for that, either before the problem was discovered or after the work
    was done. It was her decision but I suspect that after it was over
    she probably regretted it just about as much as buying something else.

    I suppose we could tell them that they really should do is go buy
    themselves new $48,000 car to fix the problem. This wouldn't be a
    problem when we all thought we were going to make more money every
    year off to infinity and we believed there would be no end to new cars.
    But as more and more sail off towards being part-time minimum wage,
    no-benefit employees I wonder where this is going to go. I fully admit
    that more and more are giving up maintenance to cover other bills.
    I've been thinking about how this could be built to make operation
    dependable and maintenance feasible.
  10. Mark Jones

    Mark Jones Guest

    Another consideration is the major pollutants emitted by the engine.
    CO2 is probably the single largest emission (aside from heat) and
    electrostatics aren't going to touch it. If the exhaust gasses could
    be cooled to -98°F then the CO2 would precipitate out as "snow" - but
    even then, there is no place cold enough to store it for any period of
    time. The best solution might be to reformulate it into something else.

    I'm not sure if simple hydrocarbons and nitrous oxides are heavy
    enough to be precipitated electrostatically. If this were the case,
    wouldn't electrostatic emissions controls already be in place?

    -- "I can conceptualize what infinity is, but I cannot imagine it."
    MCJ 200406
  11. Don Taylor

    Don Taylor Guest

    I was limiting myself to particulates. For CO2, turning it into
    limestone is probably the best solution, but I wasn't considering that.
    I was only considering particulate carbon/hydrocarbon. Gasses like
    hydrocarbons and nitrous oxides wouldn't be touched by electrostatics,
    unless they might perhaps be easily charged. And I didn't even realize
    there were electrostatic emissions controls already in place.

  12. Adam

    Adam Guest

    Thanks for the info. Are you sure that the precipitator would need to
    use DC current? I read that a corona happens more easily on AC
    current, that leads me to beleive that an AC current across the mesh
    screens would more easily charge any particles. I'm not concerned with
    directing the flow of the dust, I figure the fan behind the screens
    will be strong enough to keep things moving through the screens and
    toward the target plates.

    I've built the system, it consists of a box with two parallel screens
    across the opening to the box, then several perpendicular copper plates
    that I've connected to house ground, then a bathroom ceiling fan which
    exhausts outside the box. I've ordered some diodes, but I was just
    wondering if I can hook the power supply up directly, right now, and if
    it would work.

    Also, does anyone have any ideas on how to test this, to see if it
    really is capturing dust and any other airborne particles?

  13. Robert Baer

    Robert Baer Guest

    If you see the plates and/or screens get dirty, you will *know* it is
  14. "Real" pricipitators use pulsed DC; at voltages quite a bit beyond what the
    airgap will hold - one continuously measures the Corona-current to detect
    how long the voltage can be left on before there is a flashover and step the
    pulse with back a bit. The current rises exponentially 1-2 usec before

    Usually it's an single-SCR resonant design where the resonant frequency is
    tweaked to adjust the pulse width and the trigger frequency is fixed, at
    about 1/3 of the resonance frequency - low enough to make the pulses
    discrete and to extinguish any flashover paths from the previous pulse..
  15. Adam

    Adam Guest

    I know commercial precipitators use DC, I was just wondering if it
    would work with AC current. According to the ionic breeze patent, it
    uses pulsed DC in order to move the air without a fan. I'm using a
    fan, so I was wondering if I could just run AC current between the
    screens, and if that would be able to create a strong enough field to
    charge the dust particles flying between them.

  16. Jim Thompson

    Jim Thompson Guest

    According to "Consumer Reports" the Ionic Breeze is one of the most
    over-hyped, under-performing products they've ever reviewed.

    As a result of their review, "Consumer Reports" was sued by Sharper

    Sharper Image lost! Hurrah!

    ...Jim Thompson
  17. Rich Grise

    Rich Grise Guest

    Probably not. You'll charge your stuff for a half-cycle, then 1/120 second
    later, discharging it to charge it the opposite polarity. So your
    particles will vibrate at 60 Hz.

    AC won't precipitate anything, IOW.

    Somebody was asking, "How do I know if it's working?" I'd think, if
    there's dust accumulating, it's probably working. ;-)

    Good Luck!
  18. Mark Jones

    Mark Jones Guest

    Indeed... just *try* it, and let us know what happens. Watching it happen with
    your own eyes is a lot more interesting than listening to some old dudes telling
    you how it should work.
  19. I tested an air ionizer by putting it a clear plastic pitcher, blowing
    out a matches to make smoke in it, and shining a laser pointer through
    it. Sure enough, when I plugged the air ionizer in, the smoke in the
    pitcher became turbulent and started to clear up.


    DIY Piezo-Gyro, PCB Drill Bot & More Soon!

    POLITICS, n.
    A strife of interests masquerading as a contest of principles.
    The conduct of public affairs for private advantage. - Ambrose Bierce

  20. Robert Baer

    Robert Baer Guest

    A good reason to at least give it a try...
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