Re: [TCML] Beginning Tesla Design

[jimlux <jimlux@xxxxxxxxxxxxx>]

Taylor Skidmore wrote:
> Well, no harm involved. I really want to use this Coil for a science 
> fair project. My teacher, however, wants a project that really has no 
> publicized results, so I'm having a little trouble on that end. I was 
> thinking about something along the lines of adding a second toroid, 
> letting it sit atop the first, but I really don't know what I could 
> measure, or if that's a valid project at all.. Since I will be using the 
> Coil in the fair, my budget grows exponentially, as my parents are 
> suddenly willing to donate some money, heh. Any ideas?

build and demonstrate projects do not do well in fairs, as your teacher 
has told you.  WHat you need is to either use the coil as a tool to test 
something else, or to do a parametric design study; change some part of 
the coil design systematically and see how the performance changes.


In any case, what you wind up doing has to be something that hasn't been 
done a 1000 times (e.g. colored light on plants) and something for which 
 you can make a prediction of behavior BEFORE you actually do the 
experiment.  The prediction should be based on your "book research", not 
just pulled out of thin air (as a judge at fairs, I hate seeing a 
hypothesis that runs along the lines of "I think it will get bigger", 
with no reason why they think that).


The other thing judges like to see is quantitative measurements, and 
repeated trials, with at least some simple statistics.  An appreciation 
of the uncertainty in the measurement (measurement accuracy and 
precision) is also a big plus.  If you measure the AC line voltage and 
just write down all the digits from the meter as 120.8V.. that's one 
thing.. if you look at the manual and find that the meter accuracy is 
only 5% so you write down 120V +/-6V, that's a much better statement.


Here's some suggestions.

If you build a MMC with enough capacitors, you can vary the capacitance 
of your primary circuit, and, as a result, the value of the primary 
inductace will change, to keep fres the same.  You can use one of the 
modeling programs to predict the coil behavior and see if it matches.

Likewise, you can add a second toroid to the top, which will change the 
top load capacitance.  (Your first challenge wlll be figuring how to 
measure the change).. that should change the tuning point of the primary 
for best output, which should be predictable.  SO you have a prediction 
of how much the top load changes (based on some approximation or a 
modeling program), which you can then measure.  YOu can take your 
modeled or measured change, and plug that into the modeling code and 
predict what the new primary tuning should be.


This kind of thing is generically called "model verification"... you're 
taking someone else's model and verifying that it works, which something 
important in science.  It's the whole repeatability of results by 
another scientist thing.

You could also experiment with different shaped primaries.  I assume 
you're working with a NST powered coil, so bare AWG12 house wire works 
nicely as a primary, and you can make cardboard/foamcore supports to 
make everything from a flat spiral/pancake, to a cone, to a cylinder. 
Again, there are theoretical predictions of the inductance and 
performance that you can use to check your measured data.

Looking at differences in coupling ratio (k) (how far the primary is 
from the secondary, for the most part) would be quite interesting.

---

Those are all "tinker with the coil" experiments..
Then there are "coil as a piece of experimental apparatus" experiments.. 
 I think st Elmo's fire is particularly interesting.  It's not corona 
discharge in the classical sense, but more like electrospraying of salt 
water.   You'd set a pan of salt water on top of your coil, with 
something like a piece of wood that's wetted in the middle, and fire it 
up.  You do NOT want to have actual breakout of sparks here, just the 
HV, so the adjustments will be critical.  Even more challenging will be 
figuring out how to photograph it (it's pretty faint).  If you want some 
details on the physics behind St Elmos fire, I think I wrote something 
to the list a few years back.  Actually you could put the coil upside 
down over the pan and wood, which would be grounded.

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla