shadow@reed.UUCP (Matthew Giger) (12/08/86)
Does anyone out there know much about tesla coils? They are a type of oscillation transformer and the primaries and secondaries have to resonate at certain frequencies to be effective. The few books I could find about them weren't very descriptive, so if someone could give me a hint on how to get this thing going, I would be very grateful. -- Matt Giger tektronix!reed!shadow
lee@A60.UUCP (G. Lee) (12/09/86)
In article <4815@reed.UUCP> shadow@reed.UUCP (Matthew Giger) writes: > > Does anyone out there know much about tesla coils? They are a >type of oscillation transformer and the primaries and secondaries have >to resonate at certain frequencies to be effective. The few books I >-- > Matt Giger > tektronix!reed!shadow A friend of mine and I build a tesla coil last spring with great results. The basic idea is make a air core transformer with MANY fine secondary windings and a few heavy primary windings. The materials you will need are: 1. A neon transformer with as high a power output as you can get. ( Mine was about one kilowatt or something like that) 2. A few feet of wire about the size of 110vac house wire ( I never was very good with gages of wire ) 3. LOTS of fine enamel coated wire to make the seconary coil 4. Two carriage bolts to make the spack gap. To make the secondary coil we used a cardboard tube about seven inches in diameter and eight feet tall. Starting at one end wrap the fine enamel wire around the tube till you get to the top and attach it to a nail mounted on the end of the tube. when wrapping the wire done NOT overlap the wire. The wire wrapping should form a smooth layer over the tube. Coat this wrapped tube with varnish to help prevent arcing. The primary coil is much easier. It consists of about 5 or 6 turns of the 110vac size wire around the base end (none nail end) of the secondary coil. The primary turns should be spaced about eight inches out from the secondary coil with something VERY INSULATING between them. Making the spark gap was done using two carriage bolts and a ceramic cheese crock ( Any kind of insulation and durable container should do). We drilled a hole through each side of the jar and mounted the bolts through these holes leaving about a one inch gap between the ends of the bolts in the jar. Now to connect it all together... Connect one end of the neon sign transformer output to one end of the spark gap. connect the other end of the spark gap to one end of the primary coil. connect the other end of the primary coil back to the other output terminal of the neon sign transformer. connect the base end of the secondary coil to the side of the primary coil not connected to the spark gap. If I haven't forgotten anything it should be ready to fire (pun intended) up. You should hear the spark gap crackling, if not, UNPLUG it and move the ends of the carriage bolts together and try it again. If all goes well things should start working, at least a little. try to draw a arc off the nail on the top of the secondary using a broom stick with a nail stuck into the end. If things aren't working so well, try changing the number of turns in the primary. If things are working well you'll have arcs flying everywhere. At our coils prime, we had it throwing foot and a half arcs into thin air off the nail on the top of the seconday coil ( along with small arc jumping off everything else). The more you reduce the extrainious arcing the better the whole thing will work. Good luck and BE CAREFUL Gene Lee -- Gene Lee UUCP: ...ihnp4!{meccts,dayton,rosevax}!ems!A60!lee Sperry Corporation ATT: (612) 635-6334
ron@A60.UUCP (Ron Burns) (12/09/86)
In article <823@A60.UUCP> lee@A60.UUCP (G. Lee) writes: >In article <4815@reed.UUCP> shadow@reed.UUCP (Matthew Giger) writes: >> >> Does anyone out there know much about tesla coils? They are a > > A friend of mine and I build a tesla coil last spring with great results. Um.... that would be me. Gene did forget one very important item. As a series resonant LC circuit, you need a capacitor. this is placed in series with the neon sign xfmr secondary, the spark gap, and the Tesle coil primary. I built mine from several sheets of plexiglass/aluminum foil sanwiched together it is important to have the plexiglas a few inches larger than the foil, or it will arc around the edges, and burn down. It is also a good idea to clean everything with alcohol to prevent skin oils an dirt from providing a path. at these frequencies, voltages and powers, you will see some very unusual effects, not all of which occur on top of the Tesla secondary. -- Ron Burns UUCP: ...ihnp|{rosevax,dayton,meccts}|ems!A60!ron 612 635-6042
dcm@sfsup.UUCP (12/10/86)
In article <824@A60.UUCP> ron@A60.UUCP (Ron Burns) writes: >In article <823@A60.UUCP> lee@A60.UUCP (G. Lee) writes: >>In article <4815@reed.UUCP> shadow@reed.UUCP (Matthew Giger) writes: >>> >>> Does anyone out there know much about tesla coils? They are a >> >> A friend of mine and I build a tesla coil last spring with great results. > > Um.... that would be me. > >Gene did forget one very important item. As a series resonant LC circuit, >you need a capacitor. this is placed in series with the neon sign xfmr >secondary, the spark gap, and the Tesle coil primary. > >[ description of capacitor ] Not necessarily. In fact, I would hazzard a guess that Gene could have omitted the spark gap as well and it would have still worked. Spark gaps and capacitors are there to accumulate a charge, then release it through the primary in one large burst; much like the capacitor and point in a car. The difference is that the circuit that Ron is referring to is strictly for DC power, Genes is for AC. Yes, those neon sign transformers put out AC, so you really don't even need the sparkgap. -- David C. Miller, consultant AT&T Information Systems, Unix Computing and Technology Lab 190 River Road Summit, NJ 07901 (201) 522-5149 akgua \\ burl \\ cbosgd \\ clyde +===== !sfsup!dcm ihnp4 // cuae2 // ulysses //
majka@ubc-vision.UUCP (Marc Majka) (12/11/86)
In article <823@A60.UUCP> lee@A60.UUCP (G. Lee) writes: > At our coils prime, we had it throwing foot and a half arcs into thin air Ouch! You probably also had every TV viewer and radio listener within 10 kilometers cursing you! --- Marc Majka (VE7FIZ) - UBC Laboratory for Computational Vision
davec@mhuxu.UUCP (12/12/86)
> In article <824@A60.UUCP> ron@A60.UUCP (Ron Burns) writes: > >In article <823@A60.UUCP> lee@A60.UUCP (G. Lee) writes: > >>In article <4815@reed.UUCP> shadow@reed.UUCP (Matthew Giger) writes: > >>> > >>> Does anyone out there know much about tesla coils? They are a > >> > >> A friend of mine and I build a tesla coil last spring with great results. > > > > Um.... that would be me. > > > >Gene did forget one very important item. As a series resonant LC circuit, > >you need a capacitor. this is placed in series with the neon sign xfmr > >secondary, the spark gap, and the Tesle coil primary. > > > >[ description of capacitor ] > > Not necessarily. In fact, I would hazzard a guess that Gene could have > omitted the spark gap as well and it would have still worked. > > Spark gaps and capacitors are there to accumulate a charge, then release > it through the primary in one large burst; much like the capacitor and > point in a car. The difference is that the circuit that Ron is > referring to is strictly for DC power, Genes is for AC. Yes, those > neon sign transformers put out AC, so you really don't even need the > sparkgap. > David C. Miller, consultant Not all AC is the same though. There's the matter of frequency, the ac produced by the breaking of the arc through the LC circuit is in the hundreds of kilohertz. The current produced by the neon sigh transformer is 60 Hz. Many of the more interesting effects of the Tesla coil are produced by the high frequency, not just the voltage, so you can't leave out the capacitor or the gap. The last time I built a Tesla coil I used Coke(TM) bottles filled with salt water and coated in aluminum foil for the Capacitors. This seemed to work better than any I've built using glass plates or plexiglass. (It also looks Bizarre.) I also experimented with different topology's for the circuit. Series connections, parralell's and combinations. I think the one that worked best was to have everything in paralell. I also tried two capacitors, one accross the gap, and the other accross the sign transformer. That also worked well. The tesla coil effects are quite fun. We once lined up about 10 of the neighborhood kids up (I was pretty young when I built my first Tesla coil.) and had one end of the line hold the coil, and the other end held a flourescent tube, which glowed quite brightly. It's good to remember that while you might not get shocked by the pretty spark's, they are still hot and will burn skin at the point of contact. So make contact via a metal object, like a keyring. Have fun, (and don't electrocute yourself...) Dave Caswell allegra!mhuxu!davec
keithd@cadovax.UUCP (Keith Doyle) (12/12/86)
In article <904@sfsup.UUCP> dcm@sfsup.UUCP (David C. Miller, consultant) writes: >>Gene did forget one very important item. As a series resonant LC circuit, >>you need a capacitor. this is placed in series with the neon sign xfmr >>secondary, the spark gap, and the Tesle coil primary. > >Not necessarily. In fact, I would hazzard a guess that Gene could have >omitted the spark gap as well and it would have still worked. >Spark gaps and capacitors are there to accumulate a charge, then release >it through the primary in one large burst; much like the capacitor and >point in a car. The difference is that the circuit that Ron is >referring to is strictly for DC power, Genes is for AC. Yes, those >neon sign transformers put out AC, so you really don't even need the >sparkgap. Well, except for the fact that 60 hz won't go too far in a large air-core HV coil. What you need to go through the coil is RF, and you get that via a LC circuit with the spark-gap there to provide a jolt to 'excite' it into oscillation. I've tried it without the cap and/or without the gap, and haven't gotten any secondary emissions. I'd say they were mandatory, unless you have a source of HV RF that you can pipe into the primary directly (don't I wish). If you do, and you can vary the frequency to your liking, you can observe the various types of secondary emissions that you will get depending on the frequency involved. The characteristics of the emissions can vary widely with the resulting frequency of the circuit. (but it all has to be RF pretty much). Keith Doyle # {ucbvax,ihnp4,decvax}!trwrb!cadovax!keithd # cadovax!keithd@ucla-locus.arpa
jeffw@midas.UUCP (Jeff Winslow) (12/13/86)
In article <904@sfsup.UUCP> dcm@sfsup.UUCP (David C. Miller, consultant) writes: >In article <824@A60.UUCP> ron@A60.UUCP (Ron Burns) writes: >> >>Gene did forget one very important item. As a series resonant LC circuit, >>you need a capacitor. this is placed in series with the neon sign xfmr >>secondary, the spark gap, and the Tesle coil primary. > >Not necessarily. In fact, I would hazzard a guess that Gene could have >omitted the spark gap as well and it would have still worked. > >Spark gaps and capacitors are there to accumulate a charge, then release >it through the primary in one large burst; much like the capacitor and >point in a car. The difference is that the circuit that Ron is >referring to is strictly for DC power, Genes is for AC. Yes, those >neon sign transformers put out AC, so you really don't even need the >sparkgap. I have some serious questions about this! First, neither circuit, with or without capacitor, is DC, since as you said, the power "source" (sign transformer) puts out AC. Now, I was under the impression that neon sign transformers work on 60Hz. Also that a Tesla coil uses much higher frequencies. The primary of the Tesla coil as described would have far too low an impedance at 60Hz to allow even a 1kW sign transformer to develop anywhere near its full secondary voltage. A spark gap is a great generator of wideband noise. That gets you the high frequency. The capacitor, in combination with the primary inductance of the Tesla coil and the leakage inductance of the sign transformer, makes a high-frequency resonant circuit which, among other things, keeps the sign transformer from being effectively shorted out by lower frequency currents which would otherwise flow through the spark gap. I suspect both the spark gap and capacitor are quite necessary. Corrections welcomed... Jeff Winslow
pwu@uwmacc.UUCP (Peter ) (12/13/86)
In article <904@sfsup.UUCP>, dcm@sfsup.UUCP (David C. Miller, consultant) writes: > Not necessarily [that a capacitor in series with the primary of the tesla > coil is required]. In fact, I would hazzard a guess that Gene could have > omitted the spark gap as well and it would have still worked. Hazard indeed. If he did that he'll blow out the fuse or the neon transformer in no time. Imagine shorting the output of a neon transformer (~1000 V) to the primary of the tesla coil (several feet of wire loop around air is as good as short circult to 60 Hz AC). Maybe I am wrong; someone ought to try this out :) peter /* ** ARPA: pwu@unix.macc.wisc.edu BITNET: WU at WISVMACC ** UUCP: {seismo|harvard|topaz|caip|ll-xn| <-+ ** allegra|akgua|ucbvax|bellcore|ihnp4}!uwvax!uwmacc!pwu | ** | ** Uuhosts on this line probably have faster delivery time. ---+ */
elric@csustan.UUCP (Elric of Imrryr) (12/13/86)
In article <6204@mhuxu.UUCP> davec@mhuxu.UUCP (Dave Caswell) writes: >The tesla coil effects are quite fun. We once lined up about 10 of >the neighborhood kids up (I was pretty young when I built my first >Tesla coil.) and had one end of the line hold the coil, and the >other end held a flourescent tube, which glowed quite brightly. > A friend of mine who was a communication tech in the Airforce once pointed a microwave anntenna at a guy carring an arm load of flourescent tubes, which started to glow, and flicker.... The poor guy dropped the entire load a ran.... Brad -- elric Lunatic Labs @ Csustan {lll-crg,lll-lcc}!csustan!elric cryptography, terrorist, DES, drugs, cipher, secret, decode, AUTOVON NSA, CIA, NRO, KGB, GRU, Mossad, Libyan Hit Squad, assassination, OSI. The above is food for the Intelligence Agencies of the World.
jj@alice.UUCP (12/13/86)
The spark gap in a Tesla coil is essentially a high-frequency generator. If your primary (coil primary) has a decent Q, you can get essentially all of the energy into the RF band. The coil, which has a lousy coupling factor (essential to function), is only coupled decently at high frequencies that are also near a primary and secondary resonance. Even though it seems strange, putting the spark gap downstream of the capacitor still allows you to tune the primary of the coil... (the spark gap has a very quirky impedence that varies with current. That's why maximum current isn't good. ) Still, they're dangerous, and you shouldn't build them! -- TEDDYBEARS ARE FOR ALL YEAR. "Kiss me, Kate, and cursed' be he who first cries 'Enough!' " (ihnp4;allegra;research)!alice!jj
apn@nonvon.UUCP (apn) (12/15/86)
In article <904@sfsup.UUCP>, dcm@sfsup.UUCP (David C. Miller, consultant) writes: > > > >Gene did forget one very important item. As a series resonant LC circuit, > >you need a capacitor. this is placed in series with the neon sign xfmr > >secondary, the spark gap, and the Tesle coil primary. > > > >[ description of capacitor ] > > Not necessarily. In fact, I would hazzard a guess that Gene could have > omitted the spark gap as well and it would have still worked. > > Spark gaps and capacitors are there to accumulate a charge, then release > it through the primary in one large burst; much like the capacitor and > point in a car. The difference is that the circuit that Ron is > referring to is strictly for DC power, Genes is for AC. Yes, those > neon sign transformers put out AC, so you really don't even need the > sparkgap. > A spark gap is almost mandatory in either circuit! You should examine the rich RF spectrum emitted from any electrical spark. This is exactly what is needed to drive the primary of the final transformer in a tesla coil. 10 or 20 turns should do. The sec. should be several 1000 turns. Also, let me point that if one does use 60hz power WITHOUT a spark gap, you can still obtain a rather high voltage. Although nowhere near as high, since usually the final xformer is only air coupled and typically does not want to have any core material. Further, on using 60hz, you create a highly hazardouos HV on the output. 60 hz will not travel on your skin surface for example, while 20mhz will. This has to do with eddy current effects and surface propogation waves. Of course one way to omit the spark gap is to use a simple oscilator circuit... but last I checked 1000W of 10kv drive does not come in a nice small MOSFET package ( joke , ok ? ) So we are stuck using expensive transmitting tubes... further clarifaction/obfuscation on request. -- UUCP: ihnp4!ptsfa!nonvon!apn 100 Drakes Landing Road GreenBrae, CA 94904 +1 415 461 4655 {* War does not determine who is right or wrong........ only who is left *} {* Only those who attempt the absurd ... will achieve the impossible *} {* I think... I think it's in my basement... Let me go upstairs and check. *} {* -escher *} {* System down for P.M. until further notice *}
dcm@sfsup.UUCP (12/15/86)
+----------------------------------------------------------+ | ***DON'T BUILD A TESLA COIL WITHOUT CHECKING THE FACTS** | | (Do as I say, don't do as I did!!) | +----------------------------------------------------------+ In article <904@sfsup.UUCP>, I wrote that it was possible to build a tesla coil without a spark gap or capacitor. In article <675@uwmacc.UUCP> pwu@uwmacc.UUCP (Peter ) replied: > >If he did that he'll blow out the fuse or the neon transformer in no > time. >Imagine shorting the output of a neon transformer (~1000 V) to the >primary of the tesla coil (several feet of wire loop around air is as >good as short circult to 60 Hz AC). > >Maybe I am wrong; someone ought to try this out :) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ NO! NO! NO! NO! Having been properly chastized (sp?), I wish to withdraw those statements. I did this some years ago as a freshman in college and it did work. Lovely sparks and such. Fortunately, it seems someone up-stairs must have looked favorably on me and I'm still around today. (The secondary started arcing with one of the primary windings and burned through it before I could get it turned off! WHEW!) What I built was not a tesla coil, but a bodacious spark coil. Had I caught one of those lovely sparks it would have been hacker flambe'e. What follows is from of one of the letters I received. (This is real scary reading, looking back on what I did!! 8-< ) This one from tweed@apollo.UUCP (David Tweed): +--------> | | !!!! ATTEMPTING TO BUILD A 60-HZ TESLA COIL IS INCREDIBLY DANGEROUS !!!! | | True Tesla coils operate a a frequency of several megahertz (check one of |the many suggested references for the actual range). This makes the sparks |that are generated travel over the surface of, rather than through, the human |body, making them essentially harmless. This effect is known as the skin |effect. | | The purpose of the primary spark-gap in the Tesla coil is to provide lots |of high-frequency energy from the 60-Hz transformer (it arcs on each peak of |the power waveform, essentially). This energy is filtered by the resonant |circuit formed by the inductance of the primary of the Tesla coil and the |discrete capacitor. It is only this (safe) radio-frequency energy that gets |boosted by the secondary of the Tesla coil. | | All parts of the primary circuit should be treated as extremely dangerous, |as there is plenty of 60-Hz high voltage floating around, which is what is used |in electric chairs (just so you get the right mental image). +--------> Please be careful. I survived my experiment, others might not. David C. Miller, consultant AT&T Information Systems 190 River Road Summit, NJ 07901 (201) 522-5149 {allegra,burl,cbosgd,clyde,ihnp4,ulysses}!sfsup!dcm
milo@ndmath.UUCP (Greg Corson) (12/16/86)
I built a Tesla Coil when I was in High School in the early 70's. I used the popular electronics "big-tc" plans but for some reason I never got the kind of effects you people have described. My system used about 5 feet of carpet tubing for the secondary (heavy laquered cardboard about 4-5" around). There were 3 glass plate capacitors about 1.5 feet square wired in parallel, a spark gap and primary with about 10-12 turns of heavy wire. The primary was driven by a 12kv neon sign transformer. The best I ever got out of it was a 6-8 inch discharge (to a nail on a broomstick). Did I do something wrong or is my coil too small? Regarding weapons...I heard something bantered about on CNN awhile back about generating "cold implosions" by projecting "scalers". The equipment was supposed to be based on some of Tesla's work. Any idea what they are talking about. Greg Corson