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Arcing or charge propogation within a container

  1. Oct 25, 2009 #1
    Hey guys,

    I guess I should mention first that I am not a student

    I had something in mind I would like to try but have very little experience with electrical components. I also do not have the best knowledge base in electrical theory.

    Im trying to find a somewhat practical way to cause a reddish arc, Propogating from one body to another. This is occouring within an apperatus approximately 1ft^3.

    Body #1 will act as the electrode and will be moving on a track of some sort. During its circuit around this track it will approach body #2, when it approches distance x I would like it to arc to this particular body. The minimum and maximum distances of these bodies from each other are roughly 1" to 6" respectively.

    I understand Neon glows red when excited but dont understand whats involved in obtaining this reaction from an electrical standpoint. I would imagine very high voltage would be needed.

    Another possibility is a thin filiment attached to body B that would rub body A is it came by causing the discharge, I would imagine this would fascillitate substantially less of a voltage requirement. However, regardless of how this is accomplished, The visible light would need to be red and preffereably linear.

    Thanks in advance, Pete
  2. jcsd
  3. Oct 25, 2009 #2


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    If your container can be filled with some sort of fog (as a reflector), you could use a red laser diode that pulses when A is detected along the track.
  4. Oct 25, 2009 #3
    Hey thanks DLgoff, That's a great idea.

    My only thought would be the longevity of the environment, Once the container is sealed (with what ever gas/aerosol is to be used) it should not be opened for its expected life.

    I wonder if a fog of some sort as you said would be comprable to an inert gas in this application?

    Thanks again! Pete
  5. Oct 25, 2009 #4


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    Well my first thought would be to cool water saturated air to its dew point.
  6. Oct 25, 2009 #5
    You can use brute force high voltage. The gas breakdown voltage is roughly proportional to pressure, above a minimum. Here is Paschen's law and a list of parameters for many gasses, including helium and argon (but not neon?).
    In air, the breakdown voltage is roughly 10 kV per cm (I think). I can get 3-cm sparks from an old CD (capacitor discharge) automotive ignition circuit.
    Bob S
  7. Oct 25, 2009 #6
    Hey thanks for the info Bob. I am looking into maintaining a system of water vapor as well, thanks Don.

    I should have also mentioned, It is critical that the system operate at a pressure that is NOT dangerous should the reservoir fail.

    Lets say I decided to go with laser diodes as Don suggested. What sort of power supply would be necessary for this setup since:

    Bodies A and B would be slowly moving through the environment on a motorized track, I would like to attach these bodies to the track as inconspicuously as possible, most likely a very thin rod approx 2"-3" long. The power must traverse this rod in order to get to the bodies and power the Diodes. Do you think it would be ore appropriate to utilize lasers that operate in the visible light spectrum? Or would that be to power consuming? By the way, I don't see a problem with this device operating off household 110.

    Thanks again guys for the great advise! Pete
  8. Oct 25, 2009 #7
    How difficult/dangerous is this to utilize?

    I don't understand enough about electrical engineering theory to have a conceptual understanding of powering such a system. How does one go about obtaining such a high voltage without producing a dangerous level of amperage? Such a device would need to run on DC power, Would it not?

  9. Oct 25, 2009 #8


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    A simple laser pointer diode like the Sanyo DL-3148-023 for example, will operate at 2.2 volts dc typically with a continuous output of 3 milliwatts, which would be eye safe. Any small dc power supply (or battery) and the proper resistor to limit the diodes current to 20 mA would be fine. The power can be supplied through your rod/tube via a couple of small gauge wires. A sensor to detect when to fire could be done optically with a led emitter/detector module.
    Last edited: Oct 25, 2009
  10. Oct 25, 2009 #9
    When I worked on automobile ignitions ~1954-1958, I got knocked on my butt many times beacuse I was adjusting the distributor plate (points and condenser) with the ignition switch on. I learned very quickly that 300 volts can be generated across the points when they open (EE 101). In the case of the old coil-condenser-points ignition system, the current was limited to 2-4 amps by the coil primary resistance, and sometimes by an additional series resistance. In the case of my CD (capacitor discharge) system, a little dc-dc converter charges a capacitor to ~300 volts, and is shorted into the coil with a small dc pulse. Changing the capacitor will change the Coulombs that are discharged. In short, it is not lethal.
    Bob S
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