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Re: Flame Arc



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I received a note from Kevin <knardell-at-mailhost.accesscom-dot-net>

>Fr. McGahee,
>
>I enjoyed your explanation there, it makes alot of sense. Could you please
>explain what is going on when I put my caps across my neon outputs,
>everyone
>here has explained this to me but another view don't hurt. I have my caps
>across the neon outputs and two dinky series gaps on each HV line to the
>primary. I am getting results with this configuration but as everyone has
>told me I will blow my neon. WHat is going to blow it, the caps are not a
>dead short, when I move to the traditional method of putting the caps in
>series on one sire and the gaps on the other I get zero results and the
gap
>glows with a orange flame arc.
>
>Thanks
>PS by way of private mail (off topic here) I would really like to hear
about
>your lasers and other fun things:)))
>
>Thanks again!
>
>                                      Regards,
>                                            Kevin Nardelle

To Kevin and other Flame Throwers,

The fact that you are getting a FLAME instead of a regular Spark at your
spark gap tells me that you have your circuit connected wrong. I bet that
you have the transformer, capacitors, spark-gap and primary ALL connected
in series. That won't work, because the Neon transformer is being asked to
Charge the Capacitor(s) THROUGH the spark gap. The flame you are getting is
virtually the same kind of flame you would get if you were to draw an arc
Directly from the Transformer to it's Case.

What you want to do is Charge the Capacitor(s) until the voltage reaches a
certain critical value determined by the spacing of the Spark Gap. Then you
want to DUMP all this energy through the primary.

There are three basic ways that people have found to do this.

1) The method you were using previously. In this arrangement, the Capacitor
is connected in Parallel with the transformer. The Spark Gap and Primary
are connected in Series with one another, and then this series arrangement
is Paralleled across the Capacitor (/transformer combination). The
transformer charges the capacitor. When the voltage is great enough to
break down the dielectric (air) between the spark gap, the gap fires. The
gap switches to a heavily conducting mode, the stored energy from the
capacitor is delivered to the primary, and IF the circuit is properly
tuned, the secondary bursts into glorious resonance. 

This arrangement works fine IF your High Voltage Transformer consists of a
SINGLE SECONDARY winding. Most Neon sign transformers are actually
center-tapped to the
Case of the transformer.  Herein lies the problem! A Neon transformer is
NOT a SINGLE SECONDARY, but Two Secondaries Center Tapped to the Case. (See
my previous post for all the gruesome details). Remember all that energy
that we dumped INTO the system? When you have the wonderfully magnificent
lightning bolts hurling off of the TOP of your system, Guess What? RIGHT!
There has to be Another End experiencing the Opposite Side of all this
Electrical Activity. It's the BOTTOM of the secondary (Which Right Now
would be safest if it was connected very solidly to Good Old Mother Earth
(Ground)). The only way you can accomplish that is with your current wiring
arrangement is by (ultimately) tying
one of the Neon windings directly to Earth Ground. BUT, if you do THIS, you
actually have the AC Primary and One Side of the Neon connected TOGETHER,
because One Side of the AC Line is NEUTRAL, and that means Connected to
Ground. So you're thinking to yourself: "OK, so the case of the 12KV Neon
is now floating at 6KV. The transformer was DESIGNED for that amount of
voltage." NOPE!!!! It was Designed for That Kind of Voltage between the
CASE and the HV electrode, NOT between the Case and the PRIMARY!!! Now
let's assume that Sooner or Later there is arcing between the primary and
the case. Yeah, well, THAT is actually a SHORT between the Case and the
Lower HV winding. POOF! You now own HALF of a Neon transformer! By the way,
if you own a Single Secondary Transformer, please DO Connect the Case to a
good solid AC Ground if using the kind of circuit currently being
discussed. Otherwise Transients and Electrostatic Effects can
raise the Case to quite large potentials and cause arcing between the
Primary and the Case.

OK, so you see the problem with Floating the Case and decide to Ground the
Case. Now you have a DIFFERENT problem, but Still a PROBLEM. You see, you
have the Primary of the Tesla coil Directly connected to ONE of the sides
of your Neon transformer. Which is Grounded at its Center Tap. You Fire Up
your Tesla Coil. It hurls huge lightnin' bolts off into the sky. Meanwhile,
at the Opposite End of the Tesla Secondary, the Bottom of the Secondary is
frantically trying to find a Really Good Ground. But you aren't connected
to any Earth Ground THERE, because YOU have the CASE of your Transformer
Grounded. Not To Worry. Your Monstrous Tesla Coil just Happily Blasts
through (or Around) your Neon's Insulation... and another one of your pet
Neons just went Belly Up. Ain't it DISGUSTING?!!!

2) To get around the problems associated with method #1, you COULD decide
to TOTALLY ISOLATE the secondary and only have the secondary hurl electrons
from one end of the primary to the other. This works. It isn't as SPIFFY as
having a coil that hurls the lightning right out into the open air, of
course, but it Does Work. It is also AWFULLY Wimpy. And the Tesla Secondary
has this AWFUL tendency to spark over to the Primary. Sigh. So you make the
Beast into a Half Wave Resonant Coil in which the Tesla Primary is located
in the CENTER of a Dual Secondary. NOW the Two Ends of the Opposing
Secondaries work Against One Another, and there is No Sparking between
Tesla Primary and Secondaries, because what you REALLY have here is a
Modified AutoTransformer. Both Ends send out Beautiful Long Streamers. Life
Seems Good. Until Something gets closer to one Secondary than the other,
that is. Then the OTHER Secondary will retaliate by changing its tuning and
going Wimpy on you. TOUCH one end, and YOU become the nearest thing to a
ground point. If You or the Approaching Object is Grounded, then a spark
reaches over, establishes a Ground Reference, and POOF! You have recreated
problem #1 and Destroyed yet ANOTHER Neon Transformer. There has to be a
Better Way.

There is.

3) Take a Neon Transformer and connect it in PARALLEL with your Spark Gap.
Note that if you turned it on now, you would get nothing but that
disgusting 12KV Flaming Arc. FLOAT the Neon Transformer (Do NOT Ground it).
Floating a Neon transformer is ALWAYS somewhat IFFY, but this time it is
going
to be a Calculated Gamble. We are going to do Everything we can so that
Even Though it IS Floating, we don't Unnecessarily Stress it. We aren't
going to Completely Remove the Danger, but we ARE going to MINIMIZE it as
much as we can. Life is imperfect, but if all else fails, do something
else. 

For this Method you will Need TWO Capacitors instead of One. Connect One
Side of Each  Capacitor to a different  Neon Secondary. Connect the OTHER
side of Each Capacitor to a different side of the Tesla Primary. The INNER
side of the Primary SHOULD NOT BE CONNECTED TO THE BOTTOM OF THE TESLA
SECONDARY. It should be INSULATED from the Bottom of the Tesla Secondary by
a distance capable of insulating at least three times the rated capacity of
the Neon Transformer. If "retrofitting" a previously built coil, you might
want to wind several layers of good insulating material around the part of
the Secondary that comes nearest the Inner side of the Primary. The Next
Thing is VERY IMPORTANT! GROUND THE BOTTOM OF THE TESLA SECONDARY TO A GOOD
SOLID EARTH GROUND. If you forget to make this connection, the Coil will
SPEW Sparks all over the place until it MAKES its Own Connection (And burns
down your Tesla Coil, giving a whole New Meaning to the phrase: Firing Up
the Coil!)

OK, so what has all this stuff done for us? Well, by Isolating the Tesla
Secondary, we removed One of the Major Sources of Inductive Voltages and
Currents from the Power Supply Loop. The voltage difference between the
Neon Primary and the Bottom of the Tesla Secondary now approaches Zero
Volts. Our Trade-off is that now there may be a large voltage difference
between the inner winding of the Tesla Primary and the  Bottom of the Tesla
Secondary, but at least we can gain ACCESS to this area and Beef Up the
Insulation. (We can't too easily Modify the inside of the Neon Transformer,
now can we?) Another Wonderful Side Effect is that since the Tesla
Secondary is connected to EARTH, the Spectacular Effects caused by the Top
of the Tesla Secondary are Enhanced since the Really High Voltage At The
Top want to Reach Out and Touch EVERYTHING that is Connected to Earth.
How Cool!

Why did we use TWO Series Capacitors? To keep the Power Supply Unit
BALANCED, of course! If you draw the Schematic for this arrangement, you
will see that it is symmetrical. Which means that ideally it should have
Equal things happening at BOTH sides of the Neon Transformer. If ALL the
capacitance were on ONE side, the circuit would "Work" the same as far as
frequency, power, and all those things go, but the STRESSES in the circuit
would be out of balance. By BALANCING the circuit we HOPE that we will not
stress One Side of the Neon Transformer MORE than the Other Side.

WAIT A SECOND: in this design aren't we Charging the Capacitors THROUGH the
Tesla Primary? Yep. It doesn't matter at all really, since the Low
Frequency Charging Current sees the Tesla Primary as an Extremely Low
Resistance. The effects are so small I doubt if you could measure them even
if you wanted to.

YEAH, BUT WHAT ABOUT THAT SPARK GAP ***RIGHT ACROSS MY NEON SECONDARIES***?
First of all, the time that the Spark Gap spends Conducting is only a Small
Percentage of the Total Time. MOST of the time the Transformer is CHARGING
the Capacitors. The DISCHARGE Time is measured in microseconds. 

ONE More Issue Needs To Be Dealt With. Even with all the Good Stuff that we
just outlined, there are still Nasty Little Transient Voltages that we
would like to halt in their tracks. For this reason the Secondaries of the
Neon Transformer should should have some sort of filtering... at Least a
Coil, and Even Better, a Coil/Capacitor arrangement. There are really two
issues here. There is the need to SHUNT excessive stuff AROUND the
Secondaries. This can be done with a small value HV capacitor directly
across the two Neon HV terminals. (We are assuming that you have already
included the afore-mentioned filter Coils!) The Safety Gap can be placed
directly across the Neon transformer Secondaries, but in Parallel with the
Tesla Spark Gap is probably Preferable. The other issue has to do with the
Floating Case. I am inclined to NOT connect ANYTHING to the Case, and just
let the fact that there are balanced secondary windings force the case to a
midpoint voltage. Attaching a capacitor to the case, for example, would
tend to ANCHOR the supposedly Floating Case, and I'm really not sure if
that's a good idea. Just my own opinion. If you want to reduce any effects
caused by electrostatics, etc, then build the FLOATING Transformer into its
own little Faraday Cage. Actually good for safety too, especially for those
people out there who are in the bad habit of touching their transformers
while they are running. This is Definitely a No-No when running a Floating
Coil!

Just a little Side Note. The Original Tesla Coil Circuit had no electrical
connection between the Tesla Primary and Secondary. A French guy named
Oudin patented the  concept of tieing the bottom of the secondary to the
primary. Tesla had DONE that, of course, as many of his handwritten notes
of the time show, but Oudin is the guy that rushed out and got the patent
on that little aspect of Tesla Coils. The advantage that the Oudin Coil has
is that it does not NEED an  Earth Ground. Almost all modern Tesla Coils
use the Oudin configuration, even when the Secondary is grounded.

Hope this is useful to Somebody Out There, or I am wasting my time writing
this stuff!

If all else fails, try something else.
Fr. Thomas McGahee