Steve's High Voltage Page - Tesla coil construction

	! Warning !
There was a time when the following warning would not have to be written. Parents would know what their children were doing and adults would have a modicum of common sense. However, after viewing many other pages, I am reminded that this is not the case. For this reason, I will state the obvious: Tesla Coil construction and experimentation involve extreme high voltages and currents that can be a lethal hazard (This means you can DIE), not only to the experimenter, but to spectators and pets as well. Hazardous voltages may be present even after power has been removed, especially in the primary tank circuit. This hazard exists even though no contact is made with high voltage devices. In the voltage range that Tesla Coils operate, sparks can leap many feet! If you are not qualified to work with this type of equipment then DON'T. A further word about bystanders and spectators - children, especially those too young to know better, and pets can move faster than sound. You or I would not be able to live with ourselves if an innocent were to be hurt for any reason. Disclaimer The author of this web page and the site that hosts it bear no responsibility or liability of ANY kind for the use or misuse of any information contained herein. This information is presented as a diary of my experience and thoughts and is presented for it's educational value only. No commercial use may be made of this material.
! You have been warned !
(now that that's out of the way...)


The Project
Background	See what got me interested in Tesla and his marvelous coil	Nicola Tesla
Some Safety Precautions	We must NEVER forget safety
The Pole Pig	The trials and tribulations of finding a pole pig
Primary tank capacitor	A very important and critical part of the project
Primary Tank Coil	Many Options
The Spark Gap	Different types to consider
The Secondary	The Heart of the Coil
The Toroid	Tuning the Secondary

7/23/00
'Just got back from Cape Cod, Massachusetts. We spent a week watching my daughter win ribbons(13) in the Seacoast Classic AAA horse show in Bourne, watching whales, visiting Provincetown (weird place), and getting a good sunburn/tan. I have been getting lots of mail from some of you guys out there and it is all very good and helpful. Some of the best info I have been getting is not what I should be worried about, but what I should NOT be worried about. The image of what I will construct is firming up in my mind. I also spent a lot of time thinking about the spark gap. I think I would like to use a synchronous rotary gap at 3600 rpm (60 Cycles) with 4 poles. I reason that this would allow me to fire the spark gap at a particular point in the cycle. If I use a rather large diameter wheel, the rotational speed will be greater and hopefully quench the spark quicker. My concern here is: I want to, ideally, wait for the cap to charge, then at the peak, dump 100% of the stored charge into the tuned primary. If the spark is quenched too soon, some of the charge will be left in the cap only to make the transformer work to bring the cap back down to 0 Volts only to have to charge it again on the opposite voltage swing. Even if I were able to dump 100% of the charge of the cap on the peak voltage, this would also effectively short the secondary of the transformer... This doesn't sound like a good thing! DC is beginning to sound good here, and not pure DC but full wave bridge rectified DC. Let me tell you my reasoning and my idea:
7/25/00
I think it is time to get down to some specifics such as calculating values for and selecting components. I imagine this page is starting to load slowly, though. If you are interested in my component calculation and sourcing stuff, you may find it on this page.
7/27/00
After pricing high voltage bridge rectifiers, I tried thinking about alternatives. I think I may have something. How about a MECHANICAL bridge rectifier? Seems strange but is entirely feasible. I have already decided to use a synchronous spark gap. It is not much of a stretch to use a synchronous motor with a shaft extending from both ends with the spark gap breaker on one shaft and the rectifier rotor on the other. Details Here.
8/3/00
The synchronous motor idea sounds great except for one thing: I am running from a generator. Speed regulation is not that good. I have to use something more tolerant. After many letters to suppliers of High Voltage Diodes, most suppliers suggest that I don't want to really pay their high prices for specialized diode(stacks). Many were even helpful enough to suggest the I build my own stacks. I had considered this before but was trying to find an easy way out. It now looks like I will series string 40 diodes in series to get my desired diode. I will use 3 Amp at 1000 Volt diodes giving me a 40,000 volt diode with a 3 Amp rating! Using four of these I will build a Bridge Rectifier. This will have a forward drop of 28 volts or so per leg or 56 volts total. I may have to put resistors or caps across the diodes to equalize reverse voltages. I'm hoping that the RF chokes will attenuate the 100-200 KHz from the tank circuit enough so that I don't have to put caps across the diodes.
9/10/00
The fact that I haven't done much on this page doesn't mean I haven't been working on the coil. In the past week I acquired a DC server motor for my rotary spark gap, and a 280V 16A Variac for the input of the pole pig.
9/19/00
I am still in the acquisition stage. Things are moving much too slowly for me but are still progressing none the less. A couple of days ago I received my four 100KV diode sticks and this morning I got my 280 Volt 16 Amp Variac.
9/22/00
'Just received my pure tungsten welding rod to use for the spark gap (EBay is wonderful)

I will not post a monstrously long list of Tesla links as they are all over the search engines for anyone to find. However, be aware that his first name is sometimes spelled NICOLA and other times NIKOLA. I will give you one page of links to get you started: