The bifilar pancake coil at its resonant frequency

[web000x]

I am not sure how you guys are measuring the capacitance of your pancake coils but what I can say is that if you hook the leads of an LCR meter to the two terminals of the coil and set it to capacitance you are almost certainly getting an incorrect reading.  The basic problem is a capacitor has a DC open-circuit between the two terminals and a coil has a near DC short-circuit between the two terminals.

I am under the impression that capacitance and inductance meters excite the device under test with a series of discrete frequencies and measure the impedance and crunch the numbers back from that.  Honestly I am not sure what they actually do and I suspect different models and different brands do different things.  But it is safe to say that a capacitance meter is not expecting to see a near short-circuit in the device under test.

My suggestion is that a frequency sweep is the only way to measure the capacitance and then you have to crunch the numbers backwards to get the value.  I also suspect that as you sweep the frequency up that the pancake coil will manifest both series LC and parallel LC properties depending on the frequency and there might be multiple poles and zeros in the impedance as you do the frequency sweep. At higher frequencies just the proximity of your hand to the coil may affect the response.  This is all speculation on my part.  TK and others would know much more than me.

MileHigh

The test I referred to is one where the two coils in the bifilar windings are two capacitor plates.  In this configuration, you can indeed use a capacitance meter.  My coils are not pancake coils, rather bifilar solenoid coils.  I was interested in the relations between evostars coil capacitance vs some of the one's I had made.


Dave

[MileHigh]

The test I referred to is one where the two coils in the bifilar windings are two capacitor plates.  In this configuration, you can indeed use a capacitance meter.  My coils are not pancake coils, rather bifilar solenoid coils.  I was interested in the relations between evostars coil capacitance vs some of the one's I had made.

Yes I read your posting and I am aware of what you requested.  I was just making generic comments that of course would apply to solenoid coils also. I seem to vaguely recall someone doing a YouTube clip where two physically similar solenoid coils, one regular and one bifilar, were frequency swept and the bifilar one had a lower resonance frequency which is a satisfyingly expected result.

As another generic comment, one has to wonder about the coil self-capacitance because it can only exist as a very brief transient because the "plates" are really just a minuscule puff of charge on a conductor that "shorts out the plates" presumably very quickly.  In a true stand-alone self-resonating coil, there presumably would be such a minuscule amount of charge circulating back and forth that the AC current and corresponding magnetic field would probably be very very weak.  I have always speculated that Tesla's bifilar pancake coil was a big coil perhaps 12 feet in diameter.  I am not sure if there are any pictures of some in his lab.  Perhaps they self-resonated in the tens of kilohertz frequency range and were more "stable" for lack of a better term.  Perhaps that means that a small bifilar pancake coil that you see around here self-resonates in the megahertz range.  One meter corresponds to 300 megahertz.  So if your coil is made of 10 meters of wire and let's say the propagation inside the coil is 95% the speed of light, perhaps the "action" is somewhere in the tens of megahertz range.  This is all just speculation for the fun of it.

I will just repeat, I suspect that the patent by Tesla was more of an academic exercise.  I doubt that his design saw any practical use because if it did we would surely know about it.  I would also like it if there was an "end game."  You know, something like a kid takes a handful of transistors and resistors and a few LEDs and builds a 4-bit up-down digital counter - he has an end game.  What is the end game for the bifilar pancake coil?

MileHigh

[TinselKoala]

@MH, the way that the interturn capacitance of a Tesla Bifilar coil is generally measured is to break the
"crossover" series connection between the inner turn of one winding and the outer turn of the second winding
(or, in the case of solenoidal coils, between the top of one winding and the bottom of the other).
Then you have two separate lengths of wire closely adjacent, forming a capacitor in the same way as the old
"gimmick" caps of low pF values formed from a couple of short lengths of insulated wire twisted together
that we used to see in ham radios and other applications. You are entirely correct that common meters
cannot measure the capacitance of the fully-connected coil.

As usual, the capacitance thus formed is proportional to the areas of the "plates" or wires and inversely
proportional to the spacing between the wires (usually just the insulation thickness in the close-wound
TBF winding.)

But does this method actually give the true interturn capacitance that the coil has when fully connected
and in an oscillating or pulsed high voltage circuit as Tesla intended it to be used in the patent?
I'll leave the answer to that as an exercise for the readers.

As to how the meters actually measure this capacitance, there are several ways. One way is to put the
DUT in parallel with a known inductance inside the meter, and then "interrogate" the tank circuit thus
formed with a pulse and see how the tank responds -- it will "ring" at its resonant frequency -- then
the inductance can be calculated in the usual manner. Another way is, as you said, to measure the impedance
at some particular frequency or set of frequencies and calculate back from there.

And has been stated many times by now, Tesla sought to reduce the reliance upon expensive, bulky, costly
and unreliable _external_ HV capacitors for the primaries of his air-core resonating transformers ("Tesla Coils",
magnifying transmitters, etc) by raising the self-capacitance of these primaries in the manner described in
the patent. Nowadays this issue is rather moot because of advances in capacitor technology but for Tesla
it was a significant factor. So the patent is more than just an academic exercise; it had real-world implications
and applications for Tesla and other experimenters and builders of his day. Today, there is nothing a TBF
winding can do that cannot also be done with an ordinary monofilar winding and some added external capacitance.
"IN EVERY COIL...", as Tesla says in the patent.


I'm glad to see that "some people" are actually _reading_ Tesla's patent instead of snipping sections,
ignoring others and taking quotes out-of-context. Maybe what I've been telling them all along is
beginning to sink in.

As far as the comments of "NEWBIES" like this Zephir character go... I encourage them to perform their
own experiments and attempt to support their wild and non-physical claims with results of their own, rather
than spouting jargon and posting links that are irrelevant to the matters at hand. Have these people ever
actually done ANY experimentation at all, I wonder? Certainly I don't recall zeeing any reports of such from
Zephir.

Tesla would roll in his grave if he could see some of the utter BS that is spouted in his name... or maybe he'd just LOL.

[Zephir]

I encourage them to perform their own experiments and attempt to support their wild and non-physical claims with results of their own, rather than spouting jargon and posting links that are irrelevant to the matters at I encourage them to perform their own experiments and attempt to support their wild and non-physical claims with results of their own, rather than spouting jargon and posting links that are irrelevant to the matters at hand. hand.

The attitude of yours is completely imbecille. You even haven't proven my links are irrelevant to my claims and what you call jargon is normal scientific language. You can make an experiments whole your productive life, yet not to get an inch closer to actual solution of overunity, because you're ignorant in your very heart and you're blocking certain type of information in your head. You shouldn't therefore block this information for heads of other people just because of warning example of yours.

You know, I understand perfectly the problem with you. In history of science it's very common situation, when the very productive and successfull people (like the Ernst Rutherford, who was Nobelist in his young age and who is founder of atom nuclei) became soon or later a most rigid part of establishment and they blocked the further progress (for example with cold fusion). In my country I personally know many similar people like you in person - for example  this guy is very capable electrotechnician and hobbyist, who enjoys youtubers with his wild experiments. But despite (actually just because)  of it he is one of most effective and dangerous trolls regarding overunity.

His videos are most widespread overunity fakes (1, 2) at youtube, which are polluting public overunity space and which are copied with another trolls mindlessly (you can still recognize them by his voice and Slavish accent easily). In this way, just the establishment of community becomes the most prominent brake of its further progress. The number of (failed) attempts for overunity device replications (Tesla coil with bifilar for example) fools the newbies and makes false impression of your qualification for overunity subject in layman posters here. But in fact you're way more dangerous troll, than the government silencing progress of alternative energy research, because you're acting inside and within overunity community. I insist, you should be banned from here because of your counterproductive behavior here. The greatest enemies of overunity community are these most respected internal ones.

[citfta]

Zephir,

I have given you several links to real experiments that show you are clearly wrong.  You refuse to look at them.  Why?  Are you so afraid your false dogma will be shown for what it is?

Show me even one example that clearly shows the current reversing when a coil discharges.  Just one.  Not a bunch of drivel about how someone should be banned because they don't agree with you.  Show me some real evidence done in a controlled way that supports your false idea.  I know you can't do it because it is not true.  All the tests that were done in the thread I have been trying to get you to read show the current does not reverse when a coil discharges.  Only the voltage reverses because the coil becomes the source instead of the load when power is removed from the coil.

You asked were I got such a idea.  I got it from the high school physics class I took.  I got it from the college physics class I took.  I got it when I studied for my first class commercial FCC license.  I got it when I studied for my advanced class amateur radio operators license.  And I got it again when I went back to college for my electronics degree.  I also saw it in action almost every day that I worked as an electronics tech in an industrial plant for 30 years.

If anyone should be banned it is those that come here and deliberately post false information to confuse those really trying to learn.  Are you one of them?  It sure seems so because you twist everything anyone else posts.  I have heard that really dumb argument before that insists education and training gets in the way of open thinking.  That is just plain dumb.  How can you possibly know when you have discovered something new if you don't know what has already been discovered?  You can't.  And that is why we see so much foolishness on DumbTube.  Because people with no education post videos about their great discoveries and others with no education believe them.

I have spent many hours the last 10 years or so trying to help people on forums like this to learn about electronics.  I have built over 10 of the Bedini Simple School Girls circuit.  Which is not the circuit you posted when you tried to claim it was not anything like the Accutron watch circuit.  I have helped close to a hundred other people wanting to learn electronics to get their SSG to work by slowly taking them through the process of debugging their system that didn't work.

A sure sign of someone that doesn't know what they are talking about is when they attack the other person instead of the topic being discussed.  So I expect you will follow your past pattern and attack me for this post.  That is the only thing you can do because you have no evidence to back up your claim that current reverses when a coil discharges.

Carroll