tesla coil

 [ferd] Energizing a tesla coil

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Andreas		Mon, Oct 24, 9:16 AM
Hi all, I did some preliminary experiments to get into tesla coils and Don Smith stuff. I built a simple HV DC power supply constituted of a self-resonant HV tr

Gerry smokyatgroups@gmail.com via groups.io	Mon, Oct 24, 9:42 PM
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Hi Andreas,

As long as your pulse is relatively short compared to the expected ring frequency and the pulse rep freq (prf) is not too high, you should get some kind of ring from your tuned circuit.

The only thing I can think of would be excessive damping across the tuned circuit.

I would check the Q value.

To do this, use a high impedance feed from a low value capacitor or high value resistor or loose inductive coupling into your tuned circuit.

Feed in a continuous sinewave (unmodulated) CW signal.

Use a high impedance scope probe across the tuned circuit under test, say using a 10:1 probe.

Find the peak response frequency of the tuned circuit under test, note this frequency as "frequency centre" and adjust scope peak to peak amplitude for say 10 major divisions on screen.

Next adjust the input frequency downwards until the scope display drops to 7.07 divisions (hoping the input amplitude from signal source hasn't changed too much).

Record this frequency as "freq lower".

Then readjust oscillator frequency upward to beyond the centre frequency continuing until once again the scope display has dropped to 7.07 divisions peak to peak.

Record this frequency as "frequency upper"

Now subtract frequency lower from frequency upper, this will give you the bandwidth of your tuned circuit at the -3dB points (because when the voltage drops to 70.7% of 100% , it's 0.707 and 0.707 squared is 0.5 in power terms).

Next divide "frequency centre" by the bandwidth just calculated this will give you the Q value for your tuned circuit.

Hope this helps, Gerry

On Tue, Oct 25, 2022 at 1:16 AM Andreas <freeen2012@gmail.com> wrote:

Hi all,

I did some preliminary experiments to get into tesla coils and Don Smith stuff. I built a simple HV DC power supply constituted of a self-resonant HV transformer and an AVRAMENKO plug to charge a cap. I then attached different coils behind a spark gap in order to measure the resonance frequency of the coil (tank with the charged HV cap).



I do not see the expected oscillations. Theory suggests that I should see at least 20 high frequency cycles before the energy gets dissipated. But I see one short pulse only!?

Any idea why this is so? My guess would be that the energy is burned in the spark gap. But I thought the described setup was the basic idea of any tesla coil primary!?

Thanks,

 Andreas

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Andreas freeen2012@gmail.com via groups.io	Tue, Oct 25, 5:12 AM
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Hi Gerry,

As long as your pulse is relatively short compared to the expected ring frequency and the pulse rep freq (prf) is not too high, you should get some kind of ring from your tuned circuit.

The only thing I can think of would be excessive damping across the tuned circuit.

I would check the Q value.

I followed your method for determining the Q and got 

15,2V 21,6V 15.2V

14kHz 29kHz 54kHz

Q = 0.725 for the tesla coil 

and Q = 6.5 for the coil with the few thick turns. 

Wow, I wonder how tesla coils work at all at such bad Qs. That's probably why Don Smith apparently replaced them with low turn coils of thick silver wire.

Thanks,

 Andreas

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Ole onielsen@spamfilter.dk via groups.io	Tue, Oct 25, 5:55 AM
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Hi Andreas

The windings are close wound on a dielectric tube giving good capacitive coupling. Perhaps instead use a spiderweb coil. This was Tesla's best design. It looks like thick wire which also has more capacitance between the windings. Or one or more turns are shorted by a high-voltage punch through of the insulation. Use thin wire as the current is very low.

Source: https://www.electrothinks.com/2020/04/Simple-tesla-coil-with-2n2222.html

Regards
Ole

 

On Mon, Oct 24, 2022 at 07:16 AM, Andreas wrote:

Hi all,

I did some preliminary experiments to get into tesla coils and Don Smith stuff. I built a simple HV DC power supply constituted of a self-resonant HV transformer and an AVRAMENKO plug to charge a cap. I then attached different coils behind a spark gap in order to measure the resonance frequency of the coil (tank with the charged HV cap).



I do not see the expected oscillations. Theory suggests that I should see at least 20 high frequency cycles before the energy gets dissipated. But I see one short pulse only!?

Any idea why this is so? My guess would be that the energy is burned in the spark gap. But I thought the described setup was the basic idea of any tesla coil primary!?

Thanks,

Andreas

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Andreas freeen2012@gmail.com via groups.io	Tue, Oct 25, 12:58 PM
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Hi all,

since I got stuck consolidating ethon flow density with classical vector potential I spent some more time in the lab investigating Alexeys idea of an ideal current source. See attached PDF for a bunch of experiments with different coil setups.



Please ignore section 6 (work in progress) and pay special attention to section 4 in which I summarise the premise.

It turns out that standard tesla coils have such a bad Q that they seem unsuitable for the task. Tuning primary tank frequency with secondary tank frequency might help (though unfortunately very challenging since the parameters L and C can not arbitrarily be altered and at least sometimes impossible since in many setups no oscillations manifest in the primary - just one sharp pulse) but the fact remains that the resistance of a tesla coil is so high that the Q will always be very very bad.

Anyway, I like the idea of matching the quarter wave length frequency of a coil with its LC resonant frequency and thus making it draw significant current through the earth connecting no matter what (ideal current source). I would love to understand what exactly happens ether-wise around such a tuned setup. This transmission line thing might be key to success.

It turns out that my early measurements were off by a factor of 10 (wrong attenuation configured). The real current was 10 times higher and thus the setup close to unity in spite of the bad Q and sub-optimal earthing. So my current estimation is that this concept has potential.

Anyway, may be one or the other is interested in looking through my lab notes and potentially has something to add. Otherwise sorry for the noise. :-)

Best wishes,

 Andreas



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Alexey lz041z@gmail.com via groups.io	Tue, Oct 25, 2:56 PM
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Hi Andreas,

please check this https://www.overunityresearch.com/index.php?topic=4288.0

Usually Tesla coils have very high Q, you are doing something seriously
wrong if you get such low Q

Regards,

Alexey

On 25.10.2022 20.58, Andreas wrote:
> Hi all,
>
> since I got stuck consolidating ethon flow density with classical vector potential I spent some more time in the lab investigating Alexeys idea of an ideal current source. See attached PDF for a bunch of experiments with different coil setups.
>
>
>
> Please ignore section 6 (work in progress) and pay special attention to section 4 in which I summarise the premise.
>
> It turns out that standard tesla coils have such a bad Q that they seem unsuitable for the task. Tuning primary tank frequency with secondary tank frequency might help (though unfortunately very challenging since the parameters L and C can not arbitrarily be altered and at least sometimes impossible since in many setups no oscillations manifest in the primary - just one sharp pulse) but the fact remains that the resistance of a tesla coil is so high that the Q will always be very very bad.
>
> Anyway, I like the idea of matching the quarter wave length frequency of a coil with its LC resonant frequency and thus making it draw significant current through the earth connecting no matter what (ideal current source). I would love to understand what exactly happens ether-wise around such a tuned setup. This transmission line thing might be key to success.
>
> It turns out that my early measurements were off by a factor of 10 (wrong attenuation configured). The real current was 10 times higher and thus the setup close to unity in spite of the bad Q and sub-optimal earthing. So my current estimation is that this concept has potential.
>
> Anyway, may be one or the other is interested in looking through my lab notes and potentially has something to add. Otherwise sorry for the noise. :-)
>
> Best wishes,
>
>   Andreas
>
>
>
>
>
>


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Ole onielsen@spamfilter.dk via groups.io	Tue, Oct 25, 4:58 PM
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High-Q RF Coil Construction Techniques: https://hamwaves.com/coils/en/.

Regards
Ole

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Gerry smokyatgroups@gmail.com via groups.io	Tue, Oct 25, 6:33 PM
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Thanks for trying it Andreas, I'm happy you had a result even though not a good one.

When we think about Q it's basically the ratio of energy stored to energy dissipated. 

The higher the Q the more energy there is being exchanged between L and C whilst energy lost is usually mostly in stray unwanted shunt capacitance and resistance.

But the higher the Q, the harder it is to maintain resonance because the bandwidth becomes very narrow & often easily detuned by stray capacitance or reflections within the workspace.

In old days as an apprentice, we used to call Q "magnification factor".

It's especially hard to get enough reactance at audio frequencies without adding some kind of magnetic core, as we see in HiFi speaker crossover networks etc.

I think usually the Tesla coils are run at 150KHz to 200KHz where we get more inductive reactance so the air cored L value to C ratio can be higher.

Did you deliberately design the resonant tank to run at about 30KHz?  

To get down there so low with practical air inductors & low resistance, it ends up needing a lot of capacitance to resonate a smaller inductor.  

As the frequency gets up beyond 400KHz they sometimes space the turns away from each other using some type of cotton cord to reduce inter winding capacitance.

Or as Hendershot did with basket weave winding, attached is a pic of one of my attempts to resonate at 500KHz, it wasn't particularly successful either.

The spark gap is a threshold device, exhibiting negative resistance, as you know. 

This negative value R has to impact directly upon the tank circuit to overcome the inherent tanks' losses and re supply the load power.

I have no experience with Tesla coils apart from what I have read.

Gerry

On Tue, Oct 25, 2022 at 9:12 PM Andreas <freeen2012@gmail.com> wrote:

Hi Gerry,

As long as your pulse is relatively short compared to the expected ring frequency and the pulse rep freq (prf) is not too high, you should get some kind of ring from your tuned circuit.

The only thing I can think of would be excessive damping across the tuned circuit.

I would check the Q value.

I followed your method for determining the Q and got 

15,2V 21,6V 15.2V

14kHz 29kHz 54kHz

Q = 0.725 for the tesla coil 

and Q = 6.5 for the coil with the few thick turns. 

Wow, I wonder how tesla coils work at all at such bad Qs. That's probably why Don Smith apparently replaced them with low turn coils of thick silver wire.

Thanks,

 Andreas

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Andreas freeen2012@gmail.com via groups.io	Thu, Oct 27, 6:45 AM
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Hi all,

thanks for your responses and interesting references. I am still at it trying to attach a handle to all this stuff. I stumbled over this remark by Gerry.

> The spark gap is a threshold device, exhibiting negative resistance, as you know.


No, I don't know that. I have heard of it but that's not knowing. I have conducted a couple of quick experiments with a GDT and a real spark gap to confirm or disprove this. Please see attached PDF (only three pages).



Please note the hopefully telling scope shot on the last page and my attempt to explain what I have measured (last sentence).

I measure serious current through the spark but no voltage drop at all. The plasma obviously conducts the electricity well. Still, where is the energy going to?? Is it burned in the spark gap (without being measurable - no voltage drop)? Is it sent away by the coil as an EMP?

Any thoughts?

Thanks,

 Andreas









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Andreas freeen2012@gmail.com via groups.io	Thu, Oct 27, 7:01 AM
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Hi all,

this is a followup post.

The spark gap is a threshold device, exhibiting negative resistance, as you know. 

After examining the (posted) scope shot some more I realised that I actually have shown negative resistance. The voltage over the coil is actually higher that the applied voltage (due to the stored energy in the cap). This is kost interesting and at least confirms that (see picture)

is not the complete story. I am not so sure that this is caused by the spark gap but rather think that this is a feature of the coil that allows it to generate back EMF exceeding the applied voltage. 

Anyway, this leads to a voltage drop of 240V (voltage difference between UL and UC) while the current is positive. So this could be interpreted as negative resistance.

Questions:

1) Is this voltage drop really over the spark gap or rather over the leads  (wiring surely not suitable for 50A)?

2) Is UL > UC caused by the spark gap or is this an intrinsic property of the coil

3) Where is the complete energy vanishing to in half a cycle?

Regards,

 Andreas

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Alexey lz041z@gmail.com via groups.io	Thu, Oct 27, 1:35 PM
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Hi Andreas,

there are different types of discharges in gas media (e.g. air)

Usually plasma(arc) considered as a heat and emission loses. To avoid it you need speed up your pulse edge or rise voltage.

From your scope traces I guess you need 10 or 100 shorter edges.

The gap itself (construction, geometry) also have significant influence on the discharge.

region D - E - F is interesting

Regards,

Alexey

On 27.10.2022 14.45, Andreas wrote:

Hi all,

thanks for your responses and interesting references. I am still at it trying to attach a handle to all this stuff. I stumbled over this remark by Gerry.

The spark gap is a threshold device, exhibiting negative resistance, as you know. 

No, I don't know that. I have heard of it but that's not knowing. I have conducted a couple of quick experiments with a GDT and a real spark gap to confirm or disprove this. Please see attached PDF (only three pages).



Please note the hopefully telling scope shot on the last page and my attempt to explain what I have measured (last sentence). 

I measure serious current through the spark but no voltage drop at all. The plasma obviously conducts the electricity well. Still, where is the energy going to?? Is it burned in the spark gap (without being measurable - no voltage drop)? Is it sent away by the coil as an EMP?

Any thoughts?

Thanks,

 Andreas

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Gerry smokyatgroups@gmail.com via groups.io	Thu, Oct 27, 5:20 PM
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Hi Andreas,

I am not exactly sure where your measurements are being made.

But I think the change of volts (negative going) volts across the gap divided by the change of current through the gap gives the negative resistance.

So we get -ve dV / +ve dI = -ve R and the power injected is +ve dI x -ve dV, so volts times amps.

I attached a couple of very very old pics which show some measured values using spark gaps.

Sorry about my poor snipping skills back in those days.

Gerry

On Thu, Oct 27, 2022 at 11:01 PM Andreas <freeen2012@gmail.com> wrote:

Hi all,

this is a followup post.

The spark gap is a threshold device, exhibiting negative resistance, as you know. 

After examining the (posted) scope shot some more I realised that I actually have shown negative resistance. The voltage over the coil is actually higher that the applied voltage (due to the stored energy in the cap). This is kost interesting and at least confirms that (see picture)

is not the complete story. I am not so sure that this is caused by the spark gap but rather think that this is a feature of the coil that allows it to generate back EMF exceeding the applied voltage. 

Anyway, this leads to a voltage drop of 240V (voltage difference between UL and UC) while the current is positive. So this could be interpreted as negative resistance.

Questions:

1) Is this voltage drop really over the spark gap or rather over the leads  (wiring surely not suitable for 50A)?

2) Is UL > UC caused by the spark gap or is this an intrinsic property of the coil

3) Where is the complete energy vanishing to in half a cycle?

Regards,

 Andreas

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Andreas freeen2012@gmail.com via groups.io	Fri, Oct 28, 5:16 AM
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Hi Alexey and Gerry,

thanks for your hints.

there are different types of discharges in gas media (e.g. air) Usually plasma(arc) considered as a heat and emission loses. To avoid it you need speed up your pulse edge or rise voltage.

The gap itself (construction, geometry) also have significant influence on the discharge.

<th-1675923890.jpeg>

region D - E - F is interesting

This needs further investigation. I could not reproduce this DEF thing with my gaps. As far as measurement accuracy goes I had almost zero voltage drop over the gap once it had fired. 

Anyway, it took me 1-2 days of tinkering and wondering to finally discover a design flaw in my setup. This is just another example that there are no isolated systems in this universe (or just my stupidity). :-)

See short PDF with an explanation for the behaviour.

Sorry for the noise. I should have seen this right away. 

Regards,

 Andreas

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Alexey lz041z@gmail.com via groups.io	Sat, Oct 29, 1:42 PM
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Hi Andreas,

take a look on this https://www.youtube.com/watch?v=ivrd_fxLfQU

(some interesting experiments with Tesla coil)

Regards,

Alexey

On 28.10.2022 13.16, Andreas wrote:

Hi Alexey and Gerry,

thanks for your hints.

there are different types of discharges in gas media (e.g. air) Usually plasma(arc) considered as a heat and emission loses. To avoid it you need speed up your pulse edge or rise voltage.

The gap itself (construction, geometry) also have significant influence on the discharge.

<th-1675923890.jpeg>

region D - E - F is interesting

This needs further investigation. I could not reproduce this DEF thing with my gaps. As far as measurement accuracy goes I had almost zero voltage drop over the gap once it had fired. 

Anyway, it took me 1-2 days of tinkering and wondering to finally discover a design flaw in my setup. This is just another example that there are no isolated systems in this universe (or just my stupidity). :-)

See short PDF with an explanation for the behaviour.

Sorry for the noise. I should have seen this right away. 

Regards,

 Andreas

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Preview YouTube video Радиант на ТТ

Радиант на ТТ

Andreas freeen2012@gmail.com via groups.io	Thu, Nov 3, 1:47 PM (10 days ago)
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Hi all,

I conducted a couple of experiments with two kinds of tesla coils, one with thick HF wire (only 160 turns filled with ferrite) and with a classical tesla coil with many turns.

My attempts to increase the ground current (ideal power supply) were semi-successful (see pdf).



There is something I do not yet fully comprehend. If I inject a FG signal into one end of a TC and tune for resonance (quarter wave length, current node at one end, voltage node at the other end) I can determine a frequency where this happens (thus also a propagation speed for the wave).

If I then add a top load (capacitance) and retune I find a different (a lot lower resonance frequency). I understand this from a LC tank perspective (adding capacity). But how is this related to the transmission line aspect? The propagation speed for EM waves should not be influenced by a top load (be constant). But I get nothing at this old frequency with the top load attached.

I wonder how one gets quarter wave length frequency and LC tank frequency together/matched!?

What are expected earth ground currents for a tesla coil?

Thanks a lot,

 Andreas




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Ole		Thu, Nov 3, 3:53 PM (10 days ago)
Hi Andreas The capacitance between the sphere and ground or ambient is perhaps too great. Tesla talked about high inductance and low capacitance to make a good

Alexey lz041z@gmail.com via groups.io	Fri, Nov 4, 3:40 AM (9 days ago)
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Hi Andreas,

Some thoughts about your experiments from me

- I would suggest leave ferrites out for now, until you know precisely what you are doing, they just complicating things which already quite complex

- coils winding and modes: usually 1/4 and 1/2 modes used, simple one layer coil can work in both, but biffilar coil supposed to be used in 1/2 mode

- you seem to have some "extra" things around the coil (marked with red), they create serious interference, I suggest removing them and placing coil vertically

- matching/determining resonances: usually coils designed with some calculators (https://gorchilin.com/calculator/?lang=en this one is best I think, especially this https://gorchilin.com/calculator/combi?CGND=0&v=b&lang=en)

When you have new coil, take a signal generator and scan coil in wide range frequencies, then you will see all resonances and it will be easier classify them.

Good luck with this stuff, you will need lots of practice and patience ;)

Regards,

Alexey

On 3.11.2022 20.47, Andreas wrote:

Hi all,

I conducted a couple of experiments with two kinds of tesla coils, one with thick HF wire (only 160 turns filled with ferrite) and with a classical tesla coil with many turns. 

My attempts to increase the ground current (ideal power supply) were semi-successful (see pdf).



There is something I do not yet fully comprehend. If I inject a FG signal into one end of a TC and tune for resonance (quarter wave length, current node at one end, voltage node at the other end) I can determine a frequency where this happens (thus also a propagation speed for the wave).

If I then add a top load (capacitance) and retune I find a different (a lot lower resonance frequency). I understand this from a LC tank perspective (adding capacity). But how is this related to the transmission line aspect? The propagation speed for EM waves should not be influenced by a top load (be constant). But I get nothing at this old frequency with the top load attached. 

I wonder how one gets quarter wave length frequency and LC tank frequency together/matched!? 

What are expected earth ground currents for a tesla coil?

Thanks a lot,

 Andreas

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Andreas freeen2012@gmail.com via groups.io	Sat, Nov 5, 12:41 PM (8 days ago)
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Hi Ole and Alexey,

thanks a lot for your helpful hints regarding my tesla coil ventures. I will look up "frequency sweeping" in the FG manual and try to scan the full spectrum.

In the meanwhile I have read this page (use Google auto translate):

                http://samlib.ru/u/utkin_w_m/exper-2.shtml

This guy is amazing (has done tons of interesting experiments). I slowly get the idea why Tesla turned away from high frequency experiments to super fast pulsing. It seems that this has most merit and is probably the basic idea of all the Don Smith, Kapanadze,... devices out there.

This turns into an engineering challenge of how to generate super short and sharp high voltage pulses ideally without a spark gap that quickly wears out.

Regards,

 Andreas



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Andreas freeen2012@gmail.com via groups.io	Tue, Nov 8, 1:25 PM (5 days ago)
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Hi all,

inspired by Alexey's recently sent circuits I spent some more time on tesla coil tinkering. To get the frequency down to levels at which my H-Bridge still works (DC DC converts have a 1W limit) I filled the tesla coil with some ferrite again. I found a quarter wave length mode of the tesla coil to be at 160kHz.

Energizing the primary at this frequency with a few watts of power easily produces 6kV on the secondary (limit of my high voltage probe).

See PDF:




The earth ground current is 139mA. I am still looking into how this could morph into an ideal current supply. Anywam jsut wanted to report something.  :-)

Best wishes,

 Andreas



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Alexey lz041z@gmail.com via groups.io	Tue, Nov 8, 1:44 PM (5 days ago)
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Hi Andreas,

for example, if you manage now charge capacitor to 140v with your coil's ground current, you will have 19W output

charge up to 280v will give you 76W etc

Have fun,

Alexey

On 8.11.2022 21.25, Andreas wrote:

Hi all,

inspired by Alexey's recently sent circuits I spent some more time on tesla coil tinkering. To get the frequency down to levels at which my H-Bridge still works (DC DC converts have a 1W limit) I filled the tesla coil with some ferrite again. I found a quarter wave length mode of the tesla coil to be at 160kHz. 

Energizing the primary at this frequency with a few watts of power easily produces 6kV on the secondary (limit of my high voltage probe). 

See PDF:




The earth ground current is 139mA. I am still looking into how this could morph into an ideal current supply. Anywam jsut wanted to report something.  :-)

Best wishes,

 Andreas

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Andreas freeen2012@gmail.com via groups.io	Wed, Nov 9, 10:52 AM (4 days ago)
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Hi Alexey,

for example, if you manage now charge capacitor to 140v with your coil's ground current, you will have 19W outputcharge up to 280v will give you 76W etc.

I am actually charging up to 4.8kV. But the cap charge frequency goes down to 30Hz. I never get beyond 2W output wattage!? See attached PDF with lots of interesting measurements. But especially note the last section 7 (Having a FWBR in the earth ground connection). 

 

Any thoughts?

Regards,

   Andreas

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Alexey lz041z@gmail.com via groups.io	Thu, Nov 10, 12:50 AM (3 days ago)
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Hi Andreas,

what is schematic for your experiment with FWBR in the earth ground ?

I have same difficulties with your PDF as you with mine :) you doing complicated experiments for long time and omitting obvious information, but it is obvious only for you :) because you on the subject for  long time.

If capacitor charging slower than I guess your current measurements  were incorrect.

Regards,

Alexey

PS it might be better use 2 diodes instead of 4

On 9.11.2022 18.51, Andreas wrote:

Hi Alexey,

for example, if you manage now charge capacitor to 140v with your coil's ground current, you will have 19W outputcharge up to 280v will give you 76W etc.

I am actually charging up to 4.8kV. But the cap charge frequency goes down to 30Hz. I never get beyond 2W output wattage!? See attached PDF with lots of interesting measurements. But especially note the last section 7 (Having a FWBR in the earth ground connection). 

 

Any thoughts?

Regards,

   Andreas

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Andreas freeen2012@gmail.com via groups.io	Thu, Nov 10, 6:19 AM (3 days ago)
to ferd

Hi Alexey,

what is schematic for your experiment with FWBR in the earth ground ?

I have same difficulties with your PDF as you with mine :) you doing complicated experiments for long time and omitting obvious information, but it is obvious only for you :) because you on the subject for  long time.

You are so right. Sorry for providing insufficient information. EasyEDA no longer runs on my Yosemite Mac which makes it a lot harder for me to quickly sketch together a schematic. I have a new Mac that runs the current EasyEDA version but that is usually switched off (not my main work horse). This brings me back to developing my own schematics editor. I wanted to do this anyway for easy integration into Cassiopeia. But this will probably take 2 months of my time (at least). :-(

I had a FWBR in the earth ground connection (between the bottom lead of the tesla coil and ground) (<- AC conectors of the FBBR) and then a cap attached to the plus and minus connectors of the FWBR and behind the cap a spark gap for discharging (simply shorting) the cap once sufficient voltage was reached.

In the meanwhile I rearranged things according to the schematics you sent today (only two diodes). I also used batteries for the target instead of a cap which allowed me to get rid of the SG.

Please see the attached PDF (contains the circuit, the primary of the tesla coil is powered by a H-Bridge)

for the result.

The bottom line is that this does not work. A tesla coil is no ideal current source. Once you place anything into the ground connection the Q declines, so does the ground current. 

As far as I am concerned (so far) a tesla coil is good for generating high voltages and fancy sparks only. I cannot yet see how this is of any use in our endeavour.

I will probably examine sharp pulses and Don Smith stuff now (first build a pico pulser) ...

Thanks,

 Andreas

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Alexey lz041z@gmail.com via groups.io	Thu, Nov 10, 6:37 AM (3 days ago)
to ferd

Hi Andreas,

have you checked your coil resonances with signal generator ? How you can be sure that you are using a wave resonance, not LC ?

As a schematic editor - there is KiCAD for MAC, you can try it, unlikely you can make anything like this in two months :)

Regards,

Alexey

On 10.11.2022 14.19, Andreas wrote:

Hi Alexey,

what is schematic for your experiment with FWBR in the earth ground ?

I have same difficulties with your PDF as you with mine :) you doing complicated experiments for long time and omitting obvious information, but it is obvious only for you :) because you on the subject for  long time.

You are so right. Sorry for providing insufficient information. EasyEDA no longer runs on my Yosemite Mac which makes it a lot harder for me to quickly sketch together a schematic. I have a new Mac that runs the current EasyEDA version but that is usually switched off (not my main work horse). This brings me back to developing my own schematics editor. I wanted to do this anyway for easy integration into Cassiopeia. But this will probably take 2 months of my time (at least). :-(

I had a FWBR in the earth ground connection (between the bottom lead of the tesla coil and ground) (<- AC conectors of the FBBR) and then a cap attached to the plus and minus connectors of the FWBR and behind the cap a spark gap for discharging (simply shorting) the cap once sufficient voltage was reached.

In the meanwhile I rearranged things according to the schematics you sent today (only two diodes). I also used batteries for the target instead of a cap which allowed me to get rid of the SG.

Please see the attached PDF (contains the circuit, the primary of the tesla coil is powered by a H-Bridge)

for the result.

The bottom line is that this does not work. A tesla coil is no ideal current source. Once you place anything into the ground connection the Q declines, so does the ground current. 

As far as I am concerned (so far) a tesla coil is good for generating high voltages and fancy sparks only. I cannot yet see how this is of any use in our endeavour.

I will probably examine sharp pulses and Don Smith stuff now (first build a pico pulser) ...

Thanks,

 Andreas

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Andreas freeen2012@gmail.com via groups.io	Thu, Nov 10, 7:08 AM (3 days ago)
to ferd

Hi Alexey,

have you checked your coil resonances with signal generator ? How you can be sure that you are using a wave resonance, not LC ?

At the beginning of this endeavour, yes. I injected an FG sine wave into the bottom lead and measured with a scope the input voltage and the output voltage on the other end. I got a 90° phase shift between the two signals at resonance and huge voltage at the top end. I took this as quarter wave length resonance with a current node at the input (lower end) and voltage node at the top!? 

I later added top loads (capacity) to the soup. This increased the resonance frequency. This is probably because adding a top load converts the top end of the tesla coil into a current point (may be not a node but definitely a point where current can flow [in and out of the sphere]). This may shift the voltage node from the top end of the tesla coil further down (closer to the lower end) thus shortening the transmission line. Who knows? To be honest I get lost in the procedure when it comes to adding top loads. My recipe was:

1) Inject a FG sine wave at the lower end and measure voltages on the top end and the lower end. Once we have 90° phase shift and huge voltage at the top end we have identified quarter wave length frequency (and thus the propagation speed of the wave through the coil)!?

2) Somehow excite the tesla coil magnetically at this frequency at the bottom and see whether we still get huge voltage at the end!?

3) Add a top load in order to prevent sparks ...

But what top load value, which capacity (radius)? My measurements indicate that adding a top load brings you back to zero with regard to finding resonance frequency since it seems to modify the transmission line (I also would expect that since now current can flow out of the tesla coil at the top!?

So if I retune after adding a top load how do I know if this is LC or wave? 

As a schematic editor - there is KiCAD for MAC, you can try it, unlikely you can make anything like this in two months :)

I tried KiCAD in the past but did not really get warm with it. It's not really a Mac application but some unloved port. My plan is not to develop a full-featured schema and PCB editor. This would take years. Once I have to prepare something for JLPCB I will continue to use EasyEDA on the other Mac. What I would like to have is a tool that allows to define arbitrary components with connectors (this could be electrical components [transistor, coil, resistor,...]  or more complex components [H-Bridge, Half-Bridge, PWM-Gen,...] and the ability to link their connectors with connections. I double click on a complex component e.g. the H-Bridge should then open a new window showing the details (circuit of the H-Bridge). Ideally this should also be available as a plug-in for Cassiopeia. Having this would help me to provide more complete lab protocols. :-)

This should not take years. In a perfect world I would slip in this project right away to be more efficient afterwards. But I am not sure whether that's wise right now considering the current state of the world (all going crazy). :-(

Thanks,

 Andreas

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Alexey lz041z@gmail.com via groups.io	Thu, Nov 10, 7:35 AM (3 days ago)
to ferd

Hi Andreas,

if you have properly designed coil you will see wave and LC resonances close to each other as two separate resonances,

and LC resonance will have slightly higher frequency, then by adding top capacitor you decrease LC resonance frequency to match wave resonance, as a result you get one "combined" resonance with 4x better quality factor.

For schematic drawing you can also try something like this https://www.smartdraw.com/circuit-diagram/schematic-diagram-software.htm (online tool)

Regards,

Alexey

On 10.11.2022 15.08, Andreas wrote:

Hi Alexey,

have you checked your coil resonances with signal generator ? How you can be sure that you are using a wave resonance, not LC ?

At the beginning of this endeavour, yes. I injected an FG sine wave into the bottom lead and measured with a scope the input voltage and the output voltage on the other end. I got a 90° phase shift between the two signals at resonance and huge voltage at the top end. I took this as quarter wave length resonance with a current node at the input (lower end) and voltage node at the top!? 

I later added top loads (capacity) to the soup. This increased the resonance frequency. This is probably because adding a top load converts the top end of the tesla coil into a current point (may be not a node but definitely a point where current can flow [in and out of the sphere]). This may shift the voltage node from the top end of the tesla coil further down (closer to the lower end) thus shortening the transmission line. Who knows? To be honest I get lost in the procedure when it comes to adding top loads. My recipe was:

1) Inject a FG sine wave at the lower end and measure voltages on the top end and the lower end. Once we have 90° phase shift and huge voltage at the top end we have identified quarter wave length frequency (and thus the propagation speed of the wave through the coil)!?

2) Somehow excite the tesla coil magnetically at this frequency at the bottom and see whether we still get huge voltage at the end!?

3) Add a top load in order to prevent sparks ...

But what top load value, which capacity (radius)? My measurements indicate that adding a top load brings you back to zero with regard to finding resonance frequency since it seems to modify the transmission line (I also would expect that since now current can flow out of the tesla coil at the top!?

So if I retune after adding a top load how do I know if this is LC or wave? 

As a schematic editor - there is KiCAD for MAC, you can try it, unlikely you can make anything like this in two months :)

I tried KiCAD in the past but did not really get warm with it. It's not really a Mac application but some unloved port. My plan is not to develop a full-featured schema and PCB editor. This would take years. Once I have to prepare something for JLPCB I will continue to use EasyEDA on the other Mac. What I would like to have is a tool that allows to define arbitrary components with connectors (this could be electrical components [transistor, coil, resistor,...]  or more complex components [H-Bridge, Half-Bridge, PWM-Gen,...] and the ability to link their connectors with connections. I double click on a complex component e.g. the H-Bridge should then open a new window showing the details (circuit of the H-Bridge). Ideally this should also be available as a plug-in for Cassiopeia. Having this would help me to provide more complete lab protocols. :-)

This should not take years. In a perfect world I would slip in this project right away to be more efficient afterwards. But I am not sure whether that's wise right now considering the current state of the world (all going crazy). :-(

Thanks,

 Andreas

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Andreas freeen2012@gmail.com via groups.io	Thu, Nov 10, 10:48 AM (3 days ago)
to ferd

Hi Alexey,

if you have properly designed coil

I have purchased the tesla coils here:

https://highvoltageshop.com/epages/b73088c0-9f9a-4230-9ffc-4fd5c619abc4.sf/de_DE/?ObjectPath=/Shops/

you will see wave and LC resonances close to each other as two separate resonances, 

How do we measure LC resonance? Using a LCR meter to measure the L is probably not the way to go (unreliable). May be attach a known C and the pulse the tank with a low duty cycle pulse and measure the frequency of the oscillations!?

The problem I see is that all the LC-tank stuff 

Q=CU U=LdI/dt

is valid only if Kirchhoffs law is valid (same current everywhere in a closed circuit, sum of voltages in a loop is zero). And we are now trying to conceptualise/measure LC tank resonance for a transmission line!?

and LC resonance will have slightly higher frequency,

By LC resonance you mean just the coil with its intrinsic stray capacitance?

then by adding top capacitor you decrease LC resonance frequency to match wave resonance, as a result you get one "combined" resonance with 4x better quality factor.

Hmmgh!? I still have trouble understanding what LC resonance is about to mean for a transmission line.

I just did just another experiment with two tesla coils stacked on top of each other (to get low enough frequency for the H-Bridge without using ferrite). 

2.66kV is not bad for an input of 1.6W. But what shall we do with 100mA earth ground current if the Q ist destroyed as soon as we insert anything into the ground line?

How do you calculate the Q for such a setup by the way? 

For schematic drawing you can also try something like this https://www.smartdraw.com/circuit-diagram/schematic-diagram-software.htm (online tool)

Will look into it ...

Thanks a lot,

 Andreas

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Andreas freeen2012@gmail.com via groups.io	Thu, Nov 10, 11:57 AM (3 days ago)
to ferd

Hi all,

I have conducted one further tesla coil experiment with two stacked tesla coils (1800 turns in total), powering the primary with a H-Bridge and extracting energy by placing a battery into the ground connection. The COP varies from 16% to 32% in the 1.x W ball park.



I get high voltages and probably a fairly good Q (rather narrow frequency band of action). But this is very far away from a useful device, rather a toy even if the COP were > 1.

I understand that the primary is usually excited at 2-3kV versus the 40V I am playing with. So this may make a difference. But I already see the COP significantly declining when increasing the input voltage from 10V to 40V. If this gets any better with a spark gap driven excitation circuit then probably due to the sharp current rise!?

I will look into sharp pulses now ...

Regards,

 Andreas





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Alexey lz041z@gmail.com via groups.io	Thu, Nov 10, 12:01 PM (3 days ago)
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Hi Andreas,

take a look on coils I measured some time ago (coils.pdf)

Each coil has several different resonances, they also change when you connecting ground.

LC resonance will de-tune when you touch coil with hand, wave resonance not, half wave resonance even grow in amplitude.

I attaching a video transcript with some explanations where all different resonances come from

This subject is not very well understood (and covered by the books)

Regards,

Alexey

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Andreas freeen2012@gmail.com via groups.io	Thu, Nov 10, 1:13 PM (3 days ago)
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Hi Alexey,

take a look on coils I measured some time ago (coils.pdf)

Thanks a lot for this testing report. It's not clear to me how you have measured these frequencies!? How did you excite the coils? From the pics I would guess you have energised a one loop primary with the FG. But I would be astonished if this transferred enough energy for the coil to get excited!? 

So far I always connected the ground clip of the FG to earth and the active lead of the FG to one lead of the tesla coil and then measured the voltage at the other end. But this does work for 1/4 QUARTER WAVE MEASUREMENTs ONLY (IF AT ALL).

From the video I get this circuit.

So injecting FG into one end, grounding the other end and measuring the current on both sides. That would be good for finding the half wave resonance, or?

This is all very confusing. 

Would you share the circuit/arrangement you used for all your measurements? I guess one needs a different one for finding the 1/4 and 1/2 wave frequencies!?

And shouldn't the 1/2 wave frequency not be exactly twice the 1/4 frequency? Any theory why this is not (exactly) the case?

Thanks a lot,

 Andreas

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Alexey lz041z@gmail.com via groups.io	Thu, Nov 10, 1:58 PM (3 days ago)
to ferd

Hi Andreas,

"I would guess you have energised a one loop primary with the FG. But I would be astonished if this transferred enough energy for the coil to get excited!? "

yes, you right 1 turn and 50 ohms from SG like this

you can use scope probe to see voltage maximums along the coil (do not connect probe, just keep it close)

this will work also for 1/2 resonance (voltage nodes will be on the ends of the coil when ground not connected)

setup with SG connected to one end of coil also should work fine

for biffilar coils I use this setup with current transformer (as we usually interested in current during resonance)

"And shouldn't the 1/2 wave frequency not be exactly twice the 1/4 frequency? Any theory why this is not (exactly) the case?"

in practice after 1Mhz it become nonlinear e.g 1/4 could be 1.6Mhz and 1/2 like 4.6Mhz, depends on wire/coil former material and million other factors

"How do you calculate the Q for such a setup by the way?"

I think you can just Q = Utop * I ground / P supply, or you can pulse coil with few pulses and then see how fast amplitude decaying

Regards,

Alexey

On 10.11.2022 21.13, Andreas wrote:

Hi Alexey,

take a look on coils I measured some time ago (coils.pdf)

Thanks a lot for this testing report. It's not clear to me how you have measured these frequencies!? How did you excite the coils? From the pics I would guess you have energised a one loop primary with the FG. But I would be astonished if this transferred enough energy for the coil to get excited!? 

So far I always connected the ground clip of the FG to earth and the active lead of the FG to one lead of the tesla coil and then measured the voltage at the other end. But this does work for 1/4 QUARTER WAVE MEASUREMENTs ONLY (IF AT ALL).

From the video I get this circuit.

So injecting FG into one end, grounding the other end and measuring the current on both sides. That would be good for finding the half wave resonance, or?

This is all very confusing. 

Would you share the circuit/arrangement you used for all your measurements? I guess one needs a different one for finding the 1/4 and 1/2 wave frequencies!?

And shouldn't the 1/2 wave frequency not be exactly twice the 1/4 frequency? Any theory why this is not (exactly) the case?

Thanks a lot,

 Andreas

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Alexey lz041z@gmail.com via groups.io	Thu, Nov 10, 2:07 PM (3 days ago)
to ferd

there 2 LC resonance (series and parallel) and 4 main cases with transmission line (1/4 and 1/2 for open line, 1/4 and 1/2 for shorted line)

any "long" coil will have several combinations of these 2x4 :)

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Andreas freeen2012@gmail.com via groups.io	Sat, Nov 12, 2:51 AM (1 day ago)
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Hi Alexey,

"I would guess you have energised a one loop primary with the FG. But I would be astonished if this transferred enough energy for the coil to get excited!? 

yes, you right 1 turn and 50 ohms from SG like this

Thanks a lot for all the additional information. I have been contemplating over replacement circuits for tesla coils (models) to get an idea what this LC resonance thing is all about in long coils. I believe to have a first idea (still needs refining).

It could well be that I had LC resonance only all the time. No wonder, the Q went immediately down when adding a load to the ground connection. Yes, this is rather complicated stuff and obviously not well understood. I will invest some more time into getting a better understanding of this even if the solution is probably rather with sharp pulses then with sine waves. But it will be good to have this from the table once for all. And it's definitely a nice playground for studying EM waves. :-)

Best wishes,

Andreas

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Alexey lz041z@gmail.com via groups.io	Sat, Nov 12, 3:17 AM (1 day ago)
to ferd

Hi Andreas,

"the solution is probably rather with sharp pulses then with sine waves"

in my opinion solution requires both :) wave resonance "structure media" and give us a "link" with it

and sharp pulses influencing resonance system help extracting energy.

Regards,

Alexey

On 12.11.2022 10.51, Andreas wrote:

Hi Alexey,

"I would guess you have energised a one loop primary with the FG. But I would be astonished if this transferred enough energy for the coil to get excited!? 

yes, you right 1 turn and 50 ohms from SG like this

Thanks a lot for all the additional information. I have been contemplating over replacement circuits for tesla coils (models) to get an idea what this LC resonance thing is all about in long coils. I believe to have a first idea (still needs refining).

It could well be that I had LC resonance only all the time. No wonder, the Q went immediately down when adding a load to the ground connection. Yes, this is rather complicated stuff and obviously not well understood. I will invest some more time into getting a better understanding of this even if the solution is probably rather with sharp pulses then with sine waves. But it will be good to have this from the table once for all. And it's definitely a nice playground for studying EM waves. :-)

Best wishes,

Andreas

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Gerry smokyatgroups@gmail.com via groups.io	Sat, Nov 12, 3:27 PM (1 day ago)
to ferd

Hi Alexey & Andreas,

Just writing to say I am following along with your words and work.

I don't really have anything worthwhile to contribute re Tesla coils etc.

Enjoyed seeing the nodes pictured above, especially the ones on the bottom line, with 1/4 & 1/2 wave stubs.

By lengthening these lines we can make an inductance effect and shortening we can add capacitance effect.

We used to use adjustable concentric sliding coaxial stub lines to balance the UHF bridge (typically the GR1602B model) in impedance/admittance measurements.

Along with line stretchers to visually determine VSWR etc.

Sorry for noise, Gerry

On Fri, Nov 11, 2022 at 7:07 AM Alexey <lz041z@gmail.com> wrote:

there 2 LC resonance (series and parallel) and 4 main cases with transmission line (1/4 and 1/2 for open line, 1/4 and 1/2 for shorted line)

any "long" coil will have several combinations of these 2x4 :)

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