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RE: State finalist in the science fair with a Tesla Coil
Kent, Kim and the list,
There have been several postings in the past on presenting Tesla Coils at
Science Fairs (check archive)
I have been a CA State Science Fair Judge for 14 consecutive years and have
had in that time one TC that placed first.
I also sponsor and select a special unique award, The Silicon Boule Award:
http://www.usc.edu/CMSI/CalifSF/History/1997/pictures/BouleSr.html
also 1998 etc
The problem for Judges is that merely building a model, however complex, and
presenting it is not Science.
That's not to say it wasn't difficult to do or very well done or meritorious
in grand ways. -just doesn't fit guidelines
To a degree it is Engineering and some fairs acknowledge that by having
Science and Engineering as individual categories with separate evaluation
criteria - Engineering requires the model to have some practical use and
demonstrate why the model is preferable to others more conventional. The
Science path is the better supported path, I believe.
Science demands using scientific methodology to prove/disprove a hypothesis.
The hypothesis needn't be complex, a call you have to make
- a complex objective digs you a bigger hole to fill, but feels
great when (& if) you are able to fill it !
With the Tesla Coil there are many facets of its operation this could be
applied.
Its basic principles and laws should be well understood by the student and
presented well to the Judges.
The nature of using Alternating Current as a source of energy -
positive and negative charging of the primary Cap.
The Dielectric composition of the Pri Cap could be made into a
Project. The list contains much on this.
The TC resonant frequency is AC energy that must pass through the
Pri Cap's dielectric with minimum loss (Hi-Q) while being the source
of extremely high peak currents from the Plates stimulating the "flywheel
affect"
requiring very low DC & AC resistance of those metal plates.
The list concentrates on AC line as the basic energy provider
presenting special requirements on the dielectric.
The HF resonant voltage must swing equally above the
positive & below the negative peak of an AC power source.
A simpler analytical case would be the application of DC to the
primary (all discharges would be same polarity).
The repetition rate would be more easily predicted/controlled with
DC.
(AC case = more complex: static gap's unpredictable discharge
timing varies along a portion of the sine wave,
rotary - needs synchronization lock with the incoming sine wave,
rotational loading can affect timing but likely to a lesser
degree. (BIG motors lessen spark loading effect)
A study of affect of Pri/Sec coupling on performance:
Resonant primary loosely coupled to a resonant secondary whose
capacitance includes space around the Secondary+Ctop
The reason, need, special criteria for a switch to conduct extremely
high currents at high voltages and turn off -
"quench" rapidly to transfer all the energy stored in the primary
into spark discharge in the secondary and/or
how that's different than the more customary goal of an RF
generator to efficiently radiate an RF signal
long distances to a radio receiver.
This fundamental understanding provides the basis for the real Science
experimentation using carefully thought out and executed plans, daily log
record entries, data, graphs, sketches and conclusions which is the Science
Project at it best.
Many 'topics' could be chosen for investigation via the scientific method,
some are complicated and ALL require firm fundamental understanding
and
lots of intermediate hypothesizing and investigating through
experimentation, data recording and interpretation
- pick old ones, or new ones generated out of you own interests,
curiosity, and experimentation.
- an analysis of losses (most are in the gap) but an analytical
approach is needed and careful consideration of
How does one study and instrument loss as it applies to a
Tesla Coil whose desired product is Air discharge
- data tables and Graphs presenting data interpretation with
controls demonstrating science methodology
- Loaded vs Unloaded Q (first define Q: Pri, Sec, Inductor,
Capacitor, System affect of DC resistance)
remember inductive & capacitive reactance's are lossless -
only their resistance has loss & heat as a result
- the 'nature' of the arc (hint - every arc whether produced by AC
or DC source is a self oscillating entity -
(having measurable 'Peak' current, time of existence,
penetrating power, goes through air & glass, etc)
each has unique inductance and capacitance with varying
resonance's ~1 to 20Mhz not related to tesla Fres.
- the effect of input power vs output arc length (assuming controls
are applied and understood)
- the affect of the length of Secondary Winding and/or wire size
#turns and inductance relative to arc length
again the controls are important - control everything but
one variable so its contribution is the focus
That's not as easy as it sounds
- keeping in resonance: requires more/less Cpri and what
that difference contributes to new observations.
- ion channel or rep rate timing to produce extended arcs, or to
achieve 1st arc extension (a fundamental finding?)
- spark gap materials/configuration to produce the best output and
long life
Be careful that the hypothesis makes sense: hypothesizing that adding
capacitance to the pri or sec will cause loss of arc output is not effective
due to it being a fundamental property that resonance must be a control, not
a variable, unless you are trying to prove the fundamental property of
resonance. But then using the arc output may not be quantitative enough a
method or explain/demonstrate why it is. (other methods may load the
resonator too much, for example)
Apologies for the rambling - I intended more polish - but hope it helps -
don't let it weigh heavily, take any good.
The 'inside' of the secondary contains an energy field, more concentrated
than the external and probably more homogenous as its space to exist is
confined - so less likely to cause problems until you get near an end where
expansion starts.
I picture it much like a bar magnet, only that it is transitory in the order
of microseconds.
Dale L.A.,(actually R.B.) CA
-----Original Message-----
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, March 30, 1999 4:42 PM To: tesla-at-pupman-dot-com
Subject: State finalist in the science fair with a Tesla Coil
Original Poster: "Kent & Kim Schaffer" <santoken-at-bright-dot-net>
Hello all!
Well, if you can remember several weeks ago I was picking your brains
concerning my step son's science fair project, a Tesla Coil. And, as I am
also
sure you remember, it was a porject that took six months in production and
was
finished in the eleventh hour. Well anyway, he passed the judging at the
school to actually advance to the local science fair . At the science fair
he
received a superior. With this in his belt he advance to the regional
finals
held at a university. At the regionals, he competed against over 400
students
and earned another superior, scoring 78 out of a possible 80 points. Only
43
students (of all grades) advanced to the state finals. So now this 8th
grader
will be competing against over 800 students in the Ohio State finals. Boy
am I
excited, of course not as much as he is. The finals are at the Ohio Weslyan
University on the 17th of April. Anyone in the area on this date I would
look
forward to meeting you and talking "Tesla"!
Anyway, we have several things to accomplish beforehand. First, he was told
that he need to actually turn this into an experiment, which we have had a
difficult time in doing. One of the problems we've had is that how do you
use
a TC in an experiment? One of the judges suggested creating a data table on
how caps change the effect of a TC. I guess that the key is a DT (data
table). Has anyone crossed this bridge and have any sugggestions? I
suppose
we could create a DT on all the trials and errors and all the things we
tried,
I just thought I would probe your minds for something a little more
dazzling.
Second, The discharge on our unit is poor, while we've come to the
understanding it's capacitance. Currently we are running SW caps that we
fab'ed, it really matched the rest of the decor of the TC :) We are
currently
using 16 Nestea bottles (four serial bottles in a sting, four strings in
parallel), Gary Lau was kind enough to test the capacitance for us some time
ago (THANKS GARY!) and it tested .00057uF, our system is going to require 4
serial bottles in a string, and ten stings in parallel, I think. When it
comes
to series/parallel when working w/ caps I get really confused. Anyway, I
have
four caps in a series because it is WAY over the voltage needed and after
running the TC for nearly 10 minutes in one run the caps didn't even get
warm!
I really like that feeling! So tell me, are we going to throw this together
right? (with four bottles in a series to form a string and 10 strings in in
parallel).
Here is a question that is off the topic of the science fair, has anyone
done
any reasearch on what exactly is going on INSIDE the secondary on a TC?
Kent