Original poster: Ruben van de Ven <ruben@xxxxxxxxx>
Hi everyone,
I'm new to this list and new to Tesla Coils in general. So I think I
should introduce myself first (I don't know if it's common on this
list to do so.)
I'm Ruben and 17 years old, I'm from the Netherlands. I'm currently
doing my sixth and final year of secondary school. In this year I
have to work on a project (for the Dutch on this list: it is my
'profielwerkstuk'). This project has to be good before I can start my
exams. I was free to pick any subject I liked, after some
brainstorming I thought Tesla Coils would be a interesting subject,
and probably a cool new hobby too :-)
After picking the subject for my project I did some research about
Tesla Coils: I browsed the web, where I found a huge amount of sites
discussing Tesla Coils. And of course I found this list.
Another source of information I found was a man who also made a Tesla
Coil, using a description from a book about electricity 'for boys'
from 1955 (for the Dutch: 'Het Jongens Elektriciteitsboek' in a
chapter named 'Knutselwerkjes')
This book wasn't an in depth guide into Tesla Coils, it's just a
short description of how to build one. But the design of it differed
from the ones that you make, and that I see everywhere on the internet.
I think I used an English language version of the same or very
similar book at your age, but, of course,
at that time it was a brand new book.
Despite this I choose to work with this design because I saw one
working and I know the one who made it. And because he never
calculated anything on the design, I thought it wouldn't be very
necessary to do so and I can always do it afterwards and point out
some improvements in my report. That's why I never read a lot about
TCs before I started building (I know that was a bad choice :-( ) But
while working on the thing I got some questions and tried to answer
them. Then I found things like resonance frequencies and I wondered
what these values would be in my setup.
Even tough the design differed I filled in some values that might be
correct in javatc (http://www.classictesla.com/java/javatc.html) and
I shocked: it was about 80% detuned :-P
Altough this could be because of the values I filled in, it was
definitely a high value. When I tried it a second time (with slightly
different values) it said it was detuned for about 17% (which was
still marked as high)
To make it a little more clear to you I scanned some images from the design:
http://rvdven.nl/tesla/coils.jpg
http://rvdven.nl/tesla/setup.jpg
Short description of the design with the values I'm using between parentheses:
Primary:
Diameter: 17cm
Turns: 10
Wire diameter: 2-3mm (2mm)
Length: 15 cm
Secondary:
Diameter: 2.5-3 cm (2.5cm)
Wire diameter: 0,1 or 0.2 mm (0.2mm)
Length: 25 - 30cm (26cm)
Capacitor (I have none yet):
20 plates of glass (13x18cm) with 19 plates of tin (10x20cm of
which 10x16.5cm is between the glass plates).
Estimated thickness of the glass: ~ 3mm
I'm not sure about the capacity because I only found formulas and
constants that used inches while I'm using (centi)meters. But I
calculated it would be about 0.00428 uF (I hope this is correct,
nobody checked it yet.)
Transformer:
The original design uses a ignition coil from a car but I use a
NST: 4kV 50mA
As you can see from these images this Coil isn't grounded but has two
spheres on each end of the secondary coil. I know this will also
work, the sparks just jump from one sphere to another (given that the
two spheres are closer to each other than they are in the image.) But
this design isn't really common (for I haven't seen one yet except
the one in the book.) There must be a reason why this design isn't
used that much, and I hope you can give me this.
This design ( horizontal bipolar coil) requires near perfect
symmetry to operate efficiently
Tuning can be very tedious.
It is very prone to flashover between primary and secondary.
It is also prone to arc from the spheres back to the primary.
Another thing I was wondering is if one of you can point me to a
guide (or maybe a book) that explains how TCs work and how I should
design one. Step by step, from easy to hard. Because I found a lot of
information, most of it is pretty specialized, like: how to design a
capacitor, it's very usefull if you know how a TC works and what sort
of capacitor you need, but well, I'm not that type (yet ;-) ) The
amount of info and the language used a bit overwhelming for a newbie
like me ;-) And if such a guide/book doesn't exist, then what is the
best way to learn to design a coil. I can apply the very neat list of
formulas I found, but I guess there are more things to think about
than just formulas.
A lot of the cheap paperback reprints from the 1920s-1940s often
contain a lot of quack medicine and pseudoscientific garbage about
the medicinal properties of TCs. Even textbooks published 10-15
years ago contain some occasional mis-information that was thought
to be accurate at the time.
I was also wondering if I designing/building TCs requires a high
knowledge on electricity, because here at school we haven't had much
(only some basic things about electric engines, how to calculate
parallel/serial voltage/amperage/resistance.
Tesla Coils can be built using the "cookbook" method, but the more
you understand and know of theory the more interesting the hobby
becomes. Please read the safety info at Terry's site:
http://hot-streamer.com/TeslaCoils/TeslaCoils.htm
The last thing I would like you to ask (for now) is why there's
hardly any information about NST with a lower output than approx.
8kV. I have a 4kV/50mA NST which seems quite a high voltage for me,
but the information I can find is about at least 8kV. I understand
8kV means more fun, but why wouldn't 4kV suffice for a small design?
You can use the 4 kV NST, but:
The lower the NST output voltage, the smaller and more critical the
spark gap setting-
With 4 kV you are looking at less than 2mm maximum seperation.
The energy stored in the primary capacitor is proportional to V^2 so
at double the voltage, you can store 4 times the energy.
I'd like to thank you for reading the very long mail, and thanks in advance,
Ruben van de Ven
PS. I'm very sorry for the long read, it got a bit longer than I planned ;-)
Never be sorry for asking questions.
Matt D.