Telsa Coils
From Higher Intellect Documents
Tesla coil information Newsgroups: rec.radio.amateur.misc From: [email protected] (Paul Prescott) Subject: Re: Telsa Coils The best single source for information about Nikola Tesla, Tesla coils, and similar apparatus is: Lindsay Publications, Inc. P.O. Box 12 Bradley, IL 60915-0012 Lindsay's offers primarily reprints of books and other information concerning technology and techniques no longer in general use. Recently I noticed the book "Inventions, Researches, and Writings of Nikola Tesla" by Thomas Commerford Martin at a local bookstore. Lindsay's offers this book, but the one at the store was published by someone else, so this book is currently available from two publishers. Note: this book was originally published in 1894 and deals mostly with Tesla's work with polyphase currents and his lectures and demonstrations up to that time. There is some information on his early work with "Tesla coils", but he was actually just beginning his more famous work in this area at the time. (Tesla's Colorado Springs experiments took place in 1899-1900.) Regarding the specific questions on Tesla coil construction: There are a number of factors that need to be taken into account to get the best performance (longest sparks). One of them, the "Q", has already been mentioned. Basic rule of thumb is you want the length of the secondary coil to be 2 to 2-1/2 times the diameter. The next is a lot more tricky to work out. The length of wire used in the secondary should be equal to a quarter wavelength of the resonant frequency. This way you have a voltage maximum at the free end of the coil. From what I can tell (I've never actually built a Tesla coil due to lack of money and facilities to do the job right) this is no easy task. You have to figure out where the secondary is self-resonant, and tune the primary accordingly. Alternately, or in combination, you can tune the secondary by means of what Tesla called an "elevated capacity", those globular capacitors one often sees on the end of Tesla coil secondaries. The disadvantage of the elevated capacity is that it accumulates a charge. This should make for shorter, less continuous, less impressive discharges as opposed to a point. Also, it's quite a bit more dangerous due to the accumulated charge. The most common alternative to the single spark gap in the primary, which offers improved performance, is the rotary spark gap. This is a set of rotating contacts to increase the number of sparks and get more energy into the system. I have heard of the vacuum tube driven primary technique but I haven't heard of many successes using it. I'm figuring it's more difficult because the tube oscillator must be tuned to the frequency of the rest of the system, and this is usually not a known quantity until after everything has been tuned up and operating. I hope this information is of some use, and again I apologize for taking up so much space on a (somewhat) unrelated topic. Is there a Tesla mailing list, or enough interest to start a newsgroup? :) Paul Prescott N1AAC [email protected] From: [email protected] (Myron A. Calhoun) Newsgroups: rec.radio.amateur.misc Subject: Here is a TV flyback Tesla design While cleaning up my workroom I found a schematic for a "TESLA COIL KIT" sold (many years ago) by B & F Enterprises, 119 Foster Street, Peabody, Massachusetts 01960 (617) 531-5774: O CAP terminal (VERY HIGH VOLTAGE!) +--------------------------------+ | | +------------+ | | | | / | | | | |/ | | || $ ******** DANGER ******* +--------| | L2 = $ || $ * * 2N3055 |\ L1 = 4 $ 10 $ || $ L3 * I TAKE ABSOLUTELY * | v turns $ turns$ || $ is a * * | $ $ || $ fly- * ** NO ** * +---+ +--$ +--$ || $ back * * | | | $ | $ || $ xfrmr * RESPONSIBILITY FOR * | ^ | | $ | $ || $ * YOUR USE OR ABUSE * 2N3055 |/ | | $ | $ || $ * OF THIS CIRCUIT!!! * +--------| | | | | $ || $ * * | |\ | | | | | || $ ******** DANGER ******* | | \ | | | | | | | +--|------|--+ | | +------o 1 8 - 5 Pin connections +--------------|------|-------|--+ +-----o 8 7 5 4 to the following | | | +----o 5 6 6 2 flyback | | | +---o 7 4 8 1 transformers: | | | | | | | +-- 738192 +------|-------|-----------| | | +----- 32-10008-4 |27 ohm|240 ohm| | | +-------- 32-10014-1 +--R1--+---R2--+ | +----------- 32-8859 | | ----- | | ///// - 12 volts + Quoting from the instructions: "WE TAKE NO RESPONSIBILITY FOR YOUR ACTIONS!!! The new windings must be added to the flyback transformer to allow adequate transistor drive capability. These windings are hand wound on the bottom leg of the ferrite core where the original filament winding was located. Remove and discard the original filament winding. In its place, wind first a ten turn, center-tapped, winding using approximately 30 inches of #20 or larger hookup wire. This is easily accomplished by winding five turns at one end of the core and then twisting a loop in the free end before adding the second five turns. The complete ten-turn winding should then be held in place with a turn or two of electrical tape with the two ends and the center loop all protruding. Connection can be made to the center loop when the insulation has been carefully removed. If it becomes necessary to cut the center loop, be sure that the two ends are scraped and joined to form a mechanical as well as an electrical center-tap to the winding. [L2 in my drawing] "The second winding should be wound directly on top of the first but it should only have a total of four turns--two each side of the center-tap. Again, wind two turns of #20 or larger hookup wire, pull and twist a center loop, and wind the other two turns. Tape this winding in place on top of the first. Do not let the center taps of two windings touch each other but they should not be more than one quarter of an inch apart. [L1 in my drawing] "Wire the modified transformer to the transistors and the bias circuit resistors as indicated on the schematic circuit diagram. Be sure to mount the transistors on a suitable heat sink with the insulating hardware provided to protect them from over heating. Since the collector connection of these transistors is made to the case, it is necessary to keep them electrically isolated from one another and from the heat sink and insulators are provided to allow this. Heat sink area of approximately 25 square inches should be adequate. If, however, the power transistors become too hot to hold a finger on, more heat sink area should be provided. Heat sink material of one- eighth inch aluminum is desirable. "Note: If Oscillation does not start Immediately Interchange the two Transistor Base connections [capitalization as in original!] "CAUTION: LETHAL VOLTAGES ARE INHERENT IN THIS DEVICE. EXTREME CAUTION MUST BE EXERCISED TO KEEP THE FULL OUTPUT OF THIS DEVICE FROM BEING APPLIED LIMB-TO-LIMB OF ANY LIVING ANIMAL. SEVERE BURNS OR DEATH MAY RESULT FROM CONTACT WITH THE FULL OUTPUT..." There were other instructions about how much damage might accrue to a human if contact were made to the high-voltage output, so BE CAREFUL! I used one-half watt resistors for R1 (27 ohms) and R2 (240 ohms) and got a nice Jacob's ladder effect. It also wiped out most of the computer terminals in the entire building, so I couldn't run it very much! I later tried 18 volts and one resistor zapped immediately! Date: Tue, 27 Sep 1994 18:00:34 EDT From: MR GEORGE R BELL <[email protected]> To: [email protected] Subject: Error in TESLA.TXT file and more Information ----------------------------------------------------------------------- There is an error in the schematic diagram for the transistorized Tesla coil. In the configuration shown, the positive supply voltage goes through L2 to the Bases of Q1 and Q2, with the emitter grounded. This would tend to draw a very heavy current from the power supply, only limited by the resistance in L2 and the Base-Emitter junction in the transistors. R1 and R2 are the base biasing resistors. The connection between these two resistors is shown going through L1 to the collectors of the transistors. For proper operation of this circuit, the respective ends of L2 should be connected to the Collectors of the transistors, and the ends of L2 should be connected to the bases. This will allow proper biasing and oscillation of the circuit. Also, for the modern builder of Tesla Coils, the following are three books I feel are essential reading: 1) "Modern Tesla Coil Theory" by Duane A. Bylund, Tesla Book Company, P. O. Box 121873 Chula Vista CA 91912. This is the best modern book I have read on the subject of Tesla Coil Building and Theory. Covered are aspects Capacitive Discharge, Vacuum Tube, and Transistor Tesla Coils as well as basic theory. It cost about 25 dollars two years ago and is 140 pages, 8 and a half by 11 format. I recommend any potential builder obtain this book! 2) "The Tesla Coil Compendium" by Randall S. Peterson, 16671 T. R. 51, Mt. Cory OH 45868. Phone 419-358-1222. A complete description of several successful Tesla Coil projects. Very Good Info. Approx. 20 dollars 2 years ago. About 100 pages. May be available at the Tesla Book Company See 1 above) 3) "Tesla Handbook", by J. H. Couture, JHC Engineering, 10823 New Salem Point, San Diego, CA, 92126. Very Good Information with a systematic step-by-step method for construction of Tesla Coils of all sizes. Approx. 20 dollars two years ago. May be available at the Tesla Book Company See 1 above) I hope the above information is helpful. 73 de WB4GHZ, --- George From: <[email protected]> Subject: Tesla.txt To: [email protected] Date: Thu, 13 Oct 1994 19:13:22 +0100 (MEZ) ------------------------------------------------------------------------------ Hello, As to tesla coils there is a good scientific article: "A Tesla transformer high-voltage generator", C.R.J. Hoffmann Reviev of Scientific Instrumentation, Vol. 46, 1.Jan. 1975, pp1-4. 73, Moritz DL5UH The members and HQ staff would like to thank the following people for their contributions to this information file: N1AAC, W0PBV WB4GHZ DL5UH Send any additional information or changes to [email protected]. 73 from ARRL HQ.
