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RE: [usa-tesla] New Member

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  • McGalliard, Frederick B
    Hi. Bert’s input is great but I would opt, if you have the confidence in dealing with high voltages, to rectify the AC line voltage as input so the RF
    Message 1 of 9 , Apr 23, 2013
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      Hi. Bert’s input is great but I would opt, if you have the confidence in dealing with high voltages, to rectify the AC line voltage as input so the RF switching section has 2-300VDC to work with. A lot of PWM power supplies do that to avoid the front end transformer, which adds a lot of weight and volume. If you do not design your own, just picking one you feel confident building should do the trick. I just always liked the challenge of running off the rectified line. But it has been a while since I created a lot of smoke.

       

      From: usa-tesla@yahoogroups.com [mailto:usa-tesla@yahoogroups.com] On Behalf Of Bert Hickman
      Sent: Tuesday, April 23, 2013 7:35 AM
      To: usa-tesla@yahoogroups.com
      Subject: Re: [usa-tesla] New Member

       

       

      Hi Clay,

      Clayton Bonser wrote:

      >
      > Hello all,
      >
      > Just a short message by way of introduction, and a brief outline of
      > why I'm here.
      >
      > My name is Clay, and I have what might be called something of an
      > interest in all kinds of everything. My background is primarily from
      > mechanical engineering, so physics naturally is of interest too,
      > especially classical. Unfortunately I don't have a great deal of
      > knowledge about electricity, especially high voltage.
      >
      > My reason for joining this group is pretty specific. I want to learn
      > about Tesla coils, and particularly whether it is feasible and
      > practical to use a small coil to drive a plasma globe. I know this
      > may seem like small potatoes, but it's a starting point.

      A better source of information (from experienced Tesla Coilers and HV
      enthusiasts) would be the Tesla Coil Mailing List at
      http://www.pupman.com. Another possibility is the 4HV list at
      http://4hv.org. However, don't ask for detailed plans or specific
      instruction on the latter list - its against their rules... :^)

      >
      > I have found a fair few diagrams for circuits to drive plasma balls,
      > many using flyback transformers to get the high voltage required. I
      > have also come across circuits using the same transformers to drive
      > Tesla coils.

      A plasma ball can be driven from virtually any high-frequency (typically
      10's of kHz - MHz) HV source. The HV source is typically an RF power
      oscillator, a small Tesla Coil, a flyback transformer and oscillator.
      You can even drive it off an ignition coil driver, but the high voltage
      pulses may give you small electrical shocks when touching the globe.

      Plasma globes are capacitively excited. The high voltage terminal is
      usually surrounded by glass, and the internal gas discharges originate
      from the opposite surface of the glass. The discharges are technically
      called "dielectric barrier discharges". The electrically-conducting
      internal discharge forms one "plate", the glass is the dielectric, and
      the excited electrode is the other plate of a small capacitor. And,
      capacitors permit RF or pulsed currents to flow between the HV terminal
      to the gases inside the plasma globe. Various combinations of noble
      gases can be used at relatively higher pressures (up to atmospheric).
      Air can be used by partially evacuating the globe. More exotic gas
      blends may add a small amount of a halogen, such as iodine or bromine.

      >
      > So, questions-
      >
      > Can a Tesla coil be a practical source of high voltage suitable for
      > driving a plasma ball?

      Yes. However, the power must be kept low to avoid overheating the glass
      (via dielectric heating) - this can cause a local hot spot that then
      punctures the glass.

      The ball I plan on driving first is about 8
      > inches diameter, and I think filled with helium in a partial vacuum.

      This should work fine. Helium is not quite as flashy as neon, xenon, or
      krypton.

      >
      > Is there a fairly simple circuit that doesn't create redundancy? By
      > this I mean if I can use a flyback transformer to drive a globe, what
      > would be the point of using the same component to drive a coil to
      > drive a globe?

      A flyback transformer will work. However, some flyback transformers may
      contain an internal HV rectifier. This must be removed or bypassed - you
      want to drive the plasma globe directly from a pulsed AC or RF source
      for best operation.

      > With regards to the circuit, I would like if possible
      > to avoid spark gap circuits, as I will be trying for long term
      > reliability.

      Your plasma globe only needs a low power (watts - 10's of watts) source.
      No need for a noisy, NO2-generating spark gap.

      > I have seen a circuit using valves (electron tubes to
      > U.S. residents) that could be do-able. However, I'm no electronics
      > wizz by any account, and the circuit I have seen uses 120V without a
      > transformer. Here in Australia the mains voltage is 240V and I don't
      > know how to rework the diagram so local mains voltage could be used.
      > Part of the reason I would consider a valve circuit is purely
      > aesthetic.

      I'd suggest powering a solid state oscillator/transformer off a "wall
      wart" - a plug-in power supply - that way, you're working with a low
      voltage DC power supply and not dangerous line voltage.

      > I would like to create something with a bit of a
      > "scientific experiment" air to it. I don't like the ethos of the
      > steampunk movement, and would prefer all parts and construction to be
      > functional.
      >
      > I think that's enough questions for now.
      >
      > Thanks for reading, and for any help or advice in advance.
      >
      > Clay.

      Some possible circuits:

      Self-excited flyback:
      http://www.powerlabs.org/flybackdriver.htm
      http://www.personal.psu.edu/sdb229/plasma%20ball%20power%20supply.html

      Timer-driven flyback:
      http://www.eleccircuit.com/efficient-flyback-driver-circuit-by-ic-555-irf510/
      http://hackerfriendly.com/wp-content/uploads/2008/12/arc-speaker.png
      http://pe2bz.philpem.me.uk/Power/-%20HV/Hv-801-Projects/hv-page.htm (see
      High Voltage driver near bottom of page)

      Inverter circuit:
      http://users.silenceisdefeat.net/~lgtngstk/Sites/transist/transist.htm

      Bert
      --
      Bert Hickman
      Stoneridge Engineering
      http://www.capturedlightning.com
      ***********************************************************************
      World's source for "Captured Lightning" Lichtenberg Figure sculptures,
      magnetically "shrunken" coins, and scarce/out of print technical books
      ***********************************************************************

      >
      >

    • Clayton Bonser
      I d like to thank the people who have taken the time to make replies to my enquiries. To be honest though, some of the replies seem to me to be cryptic, and I
      Message 2 of 9 , Apr 24, 2013
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        I'd like to thank the people who have taken the time to make replies to my enquiries.

        To be honest though, some of the replies seem to me to be cryptic, and I can't see how they relate to my initial questions. This may be at least in part because, as I said at first, I am not very knowledgeable on the subject of electronics.

        Even so, some of what was written has prompted me to do more research, and helped me to be more refined in what I am looking for. Since my first post I have learnt a lot about thermionic emission, and the workings of radio valves.
        Now I have a very rudimentary understanding that I would probably need a diode and probably to triodes, although a pentode or two would be just as useful. The idea of a coil driven by valves is still attractive to me, partly because I can still remember when they were the dominant technology, and partly because I think their warm glow and the graceful curves of the older Bakelite based valves just looks good.

        With more web searching I have found a number of different circuits, and I'm giving them consideration. Some are for driving what would be an enormous coil for my purpose, others for smaller coils. If nothing else, figuring out how each circuit achieves its ends is interesting.

        In all, I think I might take the advice on a solid state circuit first, and look at valves further on, as they present their own high voltage and current difficulties. (One source of electrocution at a time seems a sensible path.) Probably something using a 12V D.C. power pack would make a reasonable starting point.

        Thanks again, and if anyone wants to volunteer any further advice, for instance preferred circuits for small coils, I'd be appreciative. I will also have a look at suggested web sites and other lists too.

        Regards,
        Clay.
      • McGalliard, Frederick B
        Love vacuum tubes, but they are high impedance and high voltage switches. Just because they are tough as nails, electronically that is, does not mean they can
        Message 3 of 9 , Apr 24, 2013
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          Love vacuum tubes, but they are high impedance and high voltage switches. Just because they are tough as nails, electronically that is, does not mean they can take anything you give them though. Too much current and the plates can get red hot. Might check the ham circuit for tube oscillators that would do the trick. I do think transistors are just so much simpler though.

           

          From: usa-tesla@yahoogroups.com [mailto:usa-tesla@yahoogroups.com] On Behalf Of Clayton Bonser
          Sent: Wednesday, April 24, 2013 3:43 AM
          To: usa-tesla@yahoogroups.com
          Subject: RE: [usa-tesla] New Member

           

           

          I'd like to thank the people who have taken the time to make replies to my enquiries.

          To be honest though, some of the replies seem to me to be cryptic, and I can't see how they relate to my initial questions. This may be at least in part because, as I said at first, I am not very knowledgeable on the subject of electronics.

          Even so, some of what was written has prompted me to do more research, and helped me to be more refined in what I am looking for. Since my first post I have learnt a lot about thermionic emission, and the workings of radio valves.
          Now I have a very rudimentary understanding that I would probably need a diode and probably to triodes, although a pentode or two would be just as useful. The idea of a coil driven by valves is still attractive to me, partly because I can still remember when they were the dominant technology, and partly because I think their warm glow and the graceful curves of the older Bakelite based valves just looks good.

          With more web searching I have found a number of different circuits, and I'm giving them consideration. Some are for driving what would be an enormous coil for my purpose, others for smaller coils. If nothing else, figuring out how each circuit achieves its ends is interesting.

          In all, I think I might take the advice on a solid state circuit first, and look at valves further on, as they present their own high voltage and current difficulties. (One source of electrocution at a time seems a sensible path.) Probably something using a 12V D.C. power pack would make a reasonable starting point.

          Thanks again, and if anyone wants to volunteer any further advice, for instance preferred circuits for small coils, I'd be appreciative. I will also have a look at suggested web sites and other lists too.

          Regards,
          Clay.

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