Toroidal Coils

[d3x0r]

- ammended notes -


I said the point of focus was the same in all coils, this is not true; it is the center of the torus, but is offset in progressively outer windings;  There may be a desire to keep the minor diameter at < 1/4(?) the major diameter; this will keep the focus of each loop within empty space.


Toroidal dimensions are referred to as major and minor also... so major is the radius that rotates around the vertical axis of the toroid.  The vertical axis is a pretty good reference?  then the minor radius is that  which is the area cross section; a picture worth a hundred words in this case


- Edit Added toroidal coil usage schematic; and vertical axis reference idea.



I have a single layer bifilar solenoid coil from my (pyramid generator; from that austrian(?) guy... the coils when used in a cpacitve/nidicutor mode end up being a AM frequency but anyway... ) it's 12 gauge wound on a single layer and another coil the same length of wire wound on top of that; using a square wave it stinulates voltage increase at 1Mhz like other similar toroidal coils, ( I guess; but in much more space).




I guess all of tesla's receiving coils were grounded; in my extended coil test, the last ones weren't actually connected to the signal sources either...


So... maybe dollard's LMD could be formed with these... hmm no it sort of lacks a capacitive element.




So, if there isn't a saturation point (which only ferro magnetic cores reach) there's just an ever expanding field... , how many pulses do I need to be able to hold the field open?  3 phases wouldn't seem to be enough ...


6 phases might be enough, one every 30 degrees...  wish I had a better sketch program... (or a graphing calculator; found one; Hmm ya 30 degree offset, for 6 is 180; and makes a good composite, but still collapses...


*sorry I'm just sort of thinking aloud*

[d3x0r]

This is roughly what my setup looks like.  The signal generator is a TL494 or a RIGOL 20mhz pulse genrator (+/-3V max); if it is the signal generator, it replaces everything up to the connection to L3; the air core pair L3/L4 is the first 1-1 toroidal coil....


L1-L2 pair (looks like a mangled L2 on the image I think) is a step up transformer; in my case this has a resonant frequency at 455Khz something that is hard to escape, and the ferro-magnetic core... (this is a 0-n toroid coil, that is the loops are wound entirely around the minor diameter, so the angle of their vertical axis is 90 degrees from the vertical axis; you know all loops preferaby without actually completing 1 wind around the major diameter )


L3 in any case is connected to a pulsing signal on one side and open on the other.  LEDs may be connected in series to provide a high voltage breakdown ; Neons or something otherwise may be approprite at higher levels...


The bridge rectifier to capacitive storage is only connected on one side; so could be simplified to 2 diodes I think.


the S1 and S2 are remanents of when I was testing without L1-L2 stepup; and was driving a voltage through L3 with the other end attached to power (in the place of L1); I would get back pulses that I think trigger a (collector resonant oscillator) behavior, and the NPN driving the NPN leaves the base of Q2 slightly high; so it ends up retriggering; in efforts to squelch that (the output from the TL494 is really a NPN transistor that is Q1 broken out from the signal generator itself) it has a 5V voltage regulator supply to trigger the gate of Q2 which is a parallel array of transistors/mosfets to drive heavy currents.  In http://www.youtube.com/watch?v=9xMQADpPE2U]some video closing S1 (aka attaching with a clip lead) (attaching an inductor to the gate of Q2, after already having some oscillation, non self starting) then I could get similar power with significant reduction in amp draw.


the resistor on S2 is near 0 value; as a ground sink for any stray signal from Q1;

[xee2]

The RMS voltage across an inductor is RMS amps times reactance in ohms. Thus 2 amps RMS AC will generate 2000 volts RMS across a 1000 ohm reactance. However, this voltage is pure reactive and can not do work. The power factor for an inductor and capacitor is zero. Your toroid driver circuit looks like it works by capturing the voltage spike produced when transistor turns off, much like a Joule thief. In this case the voltage across the coil depends on how fast the current turns off and the power is function of energy stored in magnetic field of coil. I would recommend using the full wave rectifier to charge the capacitors and then powering the LEDs from the capacitors. This prevents large voltage spikes from damaging the LEDs.

[d3x0r]

The RMS voltage across an inductor is RMS amps times reactance in ohms. Thus 2 amps RMS AC will generate 2000 volts RMS across a 1000 ohm reactance. However, this voltage is pure reactive and can not do work. The power factor for an inductor and capacitor is zero. Your toroid driver circuit looks like it works by capturing the voltage spike produced when transistor turns off, much like a Joule thief. In this case the voltage across the coil depends on how fast the current turns off and the power is function of energy stored in magnetic field of coil. I would recommend using the full wave rectifier to charge the capacitors and then powering the LEDs from the capacitors. This prevents large voltage spikes from damaging the LEDs.

Okay; I made a spreadsheet with the reactance calculations.  And I understand that reactance is equal for then capacitance and inductance at a resonant frequency.   Erms=Irms*R...

yes, sometimes I have the LEDs across the capacitors; because that is a 500mf 1000v capacitor, sometimes it's much easier to find resonance with just the LEDs, and later attatch the capacitor.

Another experiment today; I put a new tri-filar (2 of the phone punchdown wire, 1 20g magnet wire ) to see if there was a detectable difference between receiving gauges of wire.  I put this coil inside the 14g red-green coil mostly flattened out (the outer diameter of the smaller coil is approx the same as the inner diameter of the red/green coil expanded as much as possible.  I found a resonance at 1.25Mhz, and later at 2.5Mhz, but; In this configuration, Introducing ferrite into the center played little effect; but laying it on the junction between the inner and outer coils affected the frequency significantly.  Alignment of the driving coil and receiving coil are very significant.  Improved stability of resonance by shorting the remaining 2 windings, or combining and grounding one end.  (To reiterate a little, the signal is on one filament of the inner toroidal coil, ground is only attached on the outer toroidal coil).  I replaced the new trifilar with an older, smaller bifilar, and it experienced the same resonant frequency (which again is hints that the frequency is more a factor of the receiving coil than the exciter/primary), but it has at least a half inch of distance between the larger and smaller coils, and it also works with ground only attached on the receiving outer coil; and works better if the second winding is shorted (self induced current?).


... the magnetic field is measured in like Amp-Meters, so increasing the current increases potential voltage.


this is a combined capacitor/inductor, with larger notable effect from its inductance.  why is the connection of ground on a specific side so cricital?  maybe because it ensures more length used as a capacitance, which allows a current flow, which is what gives the magnetic field... but if that is the case, then the reduced capacitance of the 14 guauge red/green coil would have a significant drop of power...; but if that was all really true, attaching the ground to an entirely different coil should also reduce the capacitance to a point that there is no current, and no voltage result? but it does not.

I'll record this later maybe. (a few todos; use micro toroid to drive large; retest large coil alone in a contracted state; coil calculator says 24 turns at 8inches with a length of 1inch is 200uH; and 24 turns at 8 inches with a length of 8 inches is  79.4 microhenries.  which is approximately what I measure with my meter between flatened/expanded and contracted (tight center, tall loops).  (hmm at 200uH, 1Mhz, is   126.65  Picofarad, but I am attached to a scope to see this, although detaching probes does not disturb the frequencies enough to affect the output much )

But; early coils that were only 24 feet of wire (12' cw descending and 12' ccw, and shorted so the general direction around the toroid is the same direction (cw or ccw from one end to the other) transferred lots of power. 

To go back to Erms=Irms*R; I would expect Rind = Rcap, and Rind primary = Rind secondary; so what is the voltage increase?  Resonant stacking; is there a cap to resonant voltage?  I guess Emax=Imax*Rind; so what is Imax theoertical?  AWG guages of wire have a measured current they carry; but I've seen high frequency induction carry lots of power on a very thin wire....

Oh
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Edit; gotit.


So increased inductance increases Rind and decreased capacitance increases Rcap; so in the case of a tesla coil the Rind primary vs Rind seconary results in a translation in the Erms=Irms*Rsec vs Rpri


Rcap= Reactance capacitance
Rpri = Reactance Inductance Primary (exciter)

Rsec = Reactance Inductance Secondary (receiver)


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If I just attach the coil end at the collector and attach the 12V to the collector of a NPN; so the interuption is the pulse into the coil from the current stopping... would that be a good driver system?  is that closer resemblance to a spark gap a pulse driver into the coil?  Wastes a lot of current that way though...

[xee2]

So increased inductance increases Rind and decreased capacitance increases Rcap; so in the case of a tesla coil the Rind primary vs Rind seconary results in a translation in the Erms=Irms*Rsec vs Rpri


Rcap= Reactance capacitance
Rpri = Reactance Inductance Primary (exciter)

Yes. But reactance is usually written as XC annd XL. Rind is usually the DC resistance of the wire.
"RMS voltage = RMS AC current times reactance"
is usually used with sine waves.
You are also experiencing coil loading. This is where the inductance of one coil is effected by coupling to another coil. Capacitive loading is also possible.


I think you have made the circuit so complicated that it is hard to understand. Perhaps experimenting with a simple series LC circuit made by putting a simple coil in series with a capacitor on the sig gen output would make things clearer.