--- On Tue, 6/16/09, John Berry <[email protected]> wrote:
> From: John Berry <[email protected]>
> Subject: Re: [Vo]:Enough Already
> To: [email protected]
> Date: Tuesday, June 16, 2009, 8:41 PM
> Too bad about the helium ;)The
> charecteristic we want is for the plasma to be very exact
> about when it is and is not a plasma.It must
> de-excite as rapidly as possible.
> I am not sure but I'd suspect that would
> work better at higher rather than lower pressures?
Okay, reading your original post more carefully leads me to this understanding,
correct me if I'm wrong.
1. A plasma is established in a tube with a, say, glass envelope. The outside
of the envelope is metal foil. The plasma (conductive) is considered one plate
of a capacitor, with the glass as a dielectric. The foil is the second plate.
2. The plasma is switched 'off', meaning, there is no longer a conductor in the
tube, just an inert gas. The 1 terminal capacitor remaining is the foil plate
on the outside.
3. In some way power is generated by this.
The guy that suggested this to you has some odd stories, but that's okay, we're
trying to perform an experiment, which seems reasonably simple to do.
Neon gas is pretty easily excited, and only needs a moderate voltage to be
excited. The higher the frequency, the better it works. A car ignition coil can
be used to make a decent HV supply:
A timer circuit, either a 4046 VCO or a 555 timer is used to trigger the base
of a transistor or the gate of a MOSFET. This in turn dumps 12V at maybe 10A
across the primary of the ignition coil. The output HV is at whatever frequency
the 4046 or 555 is set at. These sort of HV outputs tend to be pretty fast rise
and fall deals. For 60 cycles, an ignition coil can be pulsed simply with a 600
watt light dimmer (DIAC-TRIAC) with a series capacitor to limit current. It
looks simple, but it will produce some damn nasty voltages.
At the local...uh...exotic store...they sell lights of many different kinds
for...well, I'm not sure exactly what they sell them for, but they do. One such
light bulb is like an incandescent bulb, the big globe type decorative ones
with the standard Edison screw base. But the inside is like a giant NE-2 neon.
You can get them with many different shaped electrodes... 8-balls, dice, or if
we want this thing to for sure be impressive, naked ladies. :)
Anyhow, the entire interior of the envelope will fill with a bright orange
plasma if a high frequency HV AC source is connected to it between the center
electrode and a foil wrapping on the outside. I never noticed anything
particularly unusual about this setup, but perhaps I am missing something. Is a
DC 'charge' potential supposed to be applied across the cap before the plasma
collapses, to charge the thing up?
--Kyle
