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What now? I'm new

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.

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:

Short description of the design with the values I'm using between parentheses:
    Diameter: 17cm
    Turns: 10
    Wire diameter: 2-3mm (2mm)
    Length: 15 cm
    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 corenct, nobody checked it yet.)
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.

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.

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.

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?

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 ;-)