Plasma Torid - Class E Self Resonant Dual/Stereo - Plasma Torid Build

[OmGigaTron]

I like the wand for it's emotional effect. It's exactly like doing a magic trick...

Cheers.

100% This is exactly the way it makes me feel.

I was so excited to show this globe to my granddaughter, and I told her PawPaw was making magic.
That is such a driving force behind this.

Because growing up, for me at least. "Plasma" wasn't really a real thing, and most science classes simply called it Magic.

So, that's what we are all doing here. Engineers by Day, Lightning Magicians by Night.
Casting Level 1 "Plasma Globe"


// Also,
an update on some of my progress outside of the actual build log:


I have also reached out to several people who have worked on this project and Recruited them over here.
Hopefully, we will hear from some others who have built this design and are working on it as well.

My goal is to get as many minds together in one place, to share ideas, so that we can all benefit from each other's work.
That way we are developing this thing with a wealth of knowledge and information.

Hopefully in the next few days, we will see a few new members chime in about their projects.

I have been quietly reading several of the builder's build logs here, and I am now certain I chose the right place to collaborate.
I have learned so much just by reading the DRSSTC builds, spark gap theory, and talking about capacitors in various threads.
Hopefully soon I will have some more to offer other than theory and ideas.

[sky-guided]

Heyo!
OmGigaTron reached out and suggested I hop into this thread

First: thanks so much for the kind words about my project! As a small correction though, using "she" would be a considerably more accurate way to refer to me.

 

[...]Getting a working simulation going would probably be helpful.[...]

This was absolutely essential for me. I spent a while in LTSpice dinking around with the circuit before anything else. Even just re-drawing the schematic was a good starting place.

I watched a video about plasma toroids yesterday and saw that they were starting the toroid by using a static charge ie a plastic rod rubbed with fur. I decided to set-up my toroid and see if this works.

Turns out it works quite well. I mentioned this in the YouTube video but I will repeat it here. This globe was filled by me a few years ago. It has 50 torr of xenon and works well. So higher pressures than the canonical 15 torr will work. Also I have reason to believe that baking the globe befoer filling is important. This globe was baked under vacuum for 12 hours at ~450C.

Oh rad, that's a clever way of getting an arc start. Also, what happens when you lower the drive power after the toroid is already running?

I'm definitely curious about other gas mixes in general.

So, I might as well post some progress.
[lots of photos]

Looking through the photos, is there any kind of insulation between the windings of your coil? (Is that just a placeholder demo coil?) Even if there is a thin lacquer or something, decent odds the voltage will be high enough for dielectric breakdown.

If I may make a minor suggestion, consider holding off on physicals layout / enclosure design until after you have a working circuit. Getting a working prototype is hard enough without trying to stuff it into a box, but once you have a circuit it's easy enough to dimension accordingly. Also, a sealed enclosure will probably cook your components.

[OmGigaTron]

Heyo!
OmGigaTron reached out and suggested I hop into this thread

First: thanks so much for the kind words about my project! As a small correction though, using "she" would be a considerably more accurate way to refer to me.

So sorry about that. I have edited my typo in my first post.

 

[...]Getting a working simulation going would probably be helpful.[...]

This was absolutely essential for me. I spent a while in LTSpice dinking around with the circuit before anything else. Even just re-drawing the schematic was a good starting place.

So, I might as well post some progress.
[lots of photos]

Looking through the photos, is there any kind of insulation between the windings of your coil? (Is that just a placeholder demo coil?) Even if there is a thin lacquer or something, decent odds the voltage will be high enough for dielectric breakdown.

If I may make a minor suggestion, consider holding off on physicals layout / enclosure design until after you have a working circuit. Getting a working prototype is hard enough without trying to stuff it into a box, but once you have a circuit it's easy enough to dimension accordingly. Also, a sealed enclosure will probably cook your components.

After I worked with my copper coils, I came to the same conclusion.
I realized that it was basically a single piece of copper with all the walls touching.
I have been toying around with 3d printing some spacers, to keep the copper tubing equally separated.

I didn't even give a thought to cooling.
Guess I'll start working on another update to my design, with some inlet power connections, and a few spots for front panel switches, pots, and other goodies.

I fired up LT spice, and have also used
https://www.falstad.com/circuit/
Because this lets me visually see what is happening in the circuit, and when it actually oscillates, I can view it.
This is my next big hurdle, as I don't have much time with simulation, so I should probably just sink a bunch of hours into tinkering with this design.

[alan sailer]

Sky-Guided asked,

Also, what happens when you lower the drive power after the toroid is already running?

What happens is if I raise the voltage the toroid edges down towards the inductor and gets smaller. Lowering the
voltage has the opposite effect. When I reach about 27 volts the toroid does a fun dance. It flickers out at the
top of the globe and then restarts at the bottom. It looks like the globe is blowing smoke rings. The twinging
noise the globe makes when it creates a toroid is a nice sound.

/>
Cheers.

[Michelle_]

 

[...]Getting a working simulation going would probably be helpful.[...]

This was absolutely essential for me. I spent a while in LTSpice dinking around with the circuit before anything else. Even just re-drawing the schematic was a good starting place.

Hi, thanks for joining and posting.

One thing I'm wondering is how did you evaluate the performance of the circuit in LTspice? Like, what were the target output parameters of the main coil, for example, that would be considered within range of success? I understand that the plasma is in essence part of the electrical circuit but I'm unsure of how, or whether, to quantify it.

Would you be willing to share your simulation file for a fair price (if so PM me, I'm an engineer and know the value of time and work!)

As for me, I inquired about the lead time of xenon globes then accidentally ordered a 2L globe since it was made "yesterday" (strike while the iron is hot as they say)

I've also obtained the schematic and details of the circuit from Zerg labs, a helpful basis for comparison to other schematics out there.

I'm interested in building a working circuit but also I want to bulletproof it with heat sinks, ducts, cooling fans etc... I have experience designing electronics enclosures as well as small ducting systems and will use thermal imaging. I will post what I'm up to once I make headway - maybe in a month or two.

[OmGigaTron]

As for me, I inquired about the lead time of xenon globes then accidentally ordered a 2L globe since it was made "yesterday" (strike while the iron is hot as they say)

I've also obtained the schematic and details of the circuit from Zerg labs, a helpful basis for comparison to other schematics out there.

I'm interested in building a working circuit but also I want to bulletproof it with heat sinks, ducts, cooling fans etc... I have experience designing electronics enclosures as well as small ducting systems and will use thermal imaging. I will post what I'm up to once I make headway - maybe in a month or two.

I'm so excited that more people are working on this project.
Congrats on grabbing one of the 2L globes.

I am also glad that there are other engineers with electronics design experience.

Most of the info that I have learned, has been in comparing different people's circuits.

[OmGigaTron]

So, today I took a stab at building out the circuit from sky-guided that I listed in the first post of the thread, and it is also in her build log.

In my own design, since I will be using a copper tube, with a possibly much greater inductance than the printed PCB coil, I will have to eventually adjust the tuning.

I have not yet added in the voltage taps, but for the most part, this looks accurate.
(I am not good at circuit design, so please, everyone chime in and let me know what I can do next to iterate and refine this design.)



If it would be helpful, I can export the design to share so others can load it up into LTSpice.

I have been doing a bunch more reading, and the "Tuning" of this circuit really has me interested.
I know a good bit about audio oscillators, such as LFOs, and circuits used in synthesizers.
This to me is kinda like that, but in the RF frequency range.
So I relate that to simply much higher OCTAVES, in acoustic signals.

I would really love to do something Musical with this circuit and somehow integrate an LFO that feeds/controls the timing of the oscillations.
This is all mostly speculation and theory, so if I am incorrect, or need to approach this another way let me know.
I just like thinking out loud sometimes.

[sky-guided]

One thing I'm wondering is how did you evaluate the performance of the circuit in LTspice? Like, what were the target output parameters of the main coil, for example, that would be considered within range of success? I understand that the plasma is in essence part of the electrical circuit but I'm unsure of how, or whether, to quantify it.

Would you be willing to share your simulation file for a fair price (if so PM me, I'm an engineer and know the value of time and work!)

Sure thing! LTspice file is attached.

Admittedly I never actually settled on what a good figure of merit for sim evaluation/optimization might be -- for me, most of the usefulness was in drawing the circuit for myself gaining some basic intuitions about its behavior rather than a true analysis. I also haven't really modeled the plasma secondary characteristics. Specific MOSFET and component values in the attached sim are different than my current revision.

Here's what's planned for the upcoming revision (schematic still a bit messy):


I haven't tested the twin parallel mosfets yet. Also, most of these components aren't a magic value or anything -- folks, please don't assume you'll need to use the same!

Once I've showcased my full finished version, I'll be open-sourcing this entire project.

[Michelle_]

One thing I'm wondering is how did you evaluate the performance of the circuit in LTspice? Like, what were the target output parameters of the main coil, for example, that would be considered within range of success? I understand that the plasma is in essence part of the electrical circuit but I'm unsure of how, or whether, to quantify it.

Would you be willing to share your simulation file for a fair price (if so PM me, I'm an engineer and know the value of time and work!)

Sure thing! LTspice file is attached.

Admittedly I never actually settled on what a good figure of merit for sim evaluation/optimization might be -- for me, most of the usefulness was in drawing the circuit for myself gaining some basic intuitions about its behavior rather than a true analysis. I also haven't really modeled the plasma secondary characteristics. Specific MOSFET and component values in the attached sim are different than my current revision.

Here's what's planned for the upcoming revision (schematic still a bit messy):
[img]https://i.imgur.com/fwVq476.png[/img

I haven't tested the twin parallel mosfets yet. Also, most of these components aren't a magic value or anything -- folks, please don't assume you'll need to use the same!

Once I've showcased my full finished version, I'll be open-sourcing this entire project.

Thank you for sharing the file, that's very nice and generous of you to share your work! It will be really helpful for me as far as learning what's going on here. I'm quite an electrical noob. I'm an automation and design engineer by trade and don't know much about actual electronics beyond industrial controls... yet.

[Michelle_]

As for me, I inquired about the lead time of xenon globes then accidentally ordered a 2L globe since it was made "yesterday" (strike while the iron is hot as they say)

I've also obtained the schematic and details of the circuit from Zerg labs, a helpful basis for comparison to other schematics out there.

I'm interested in building a working circuit but also I want to bulletproof it with heat sinks, ducts, cooling fans etc... I have experience designing electronics enclosures as well as small ducting systems and will use thermal imaging. I will post what I'm up to once I make headway - maybe in a month or two.

I'm so excited that more people are working on this project.
Congrats on grabbing one of the 2L globes.

I am also glad that there are other engineers with electronics design experience.

Most of the info that I have learned, has been in comparing different people's circuits.

I'm excited about it too, when I first saw a video of one of these I thought I probably wouldn't ever be able to build one but here we are.

[alan sailer]

So a few minor facts to add to the information pile.

Background, I have an old xenon globe at 50 torr that I filled long before any toroid frenzy. It
makes a good but hot toroid display.

I ordered a few more globes and filled them with 15 torr and then 50 torr xenon. No toroid
behavior. I began to wonder if baking was the difference. So I build a sketchy oven and baked a
one liter globe at 350C for an hour. Filled it with 15 torr of xenon.

Observations.

The new globe is super easy to start using the static trick.

The lower pressure globe uses less power. Still not low as some others have noted but I will not
say that my drive circuit is well tuned.

The ring in the lower pressure globe is not stable. It "attaches" itself to the coil and rolls around.

huxmans observation that the winding direction of the output coil is important is true. If I flip my
coil I can't get anything. It is pure luck that I got the right "polarity".

[OmGigaTron]

So a few minor facts to add to the information pile.

Background, I have an old xenon globe at 50 torr that I filled long before any toroid frenzy. It
makes a good but hot toroid display.

I ordered a few more globes and filled them with 15 torr and then 50 torr xenon. No toroid
behavior. I began to wonder if baking was the difference. So I build a sketchy oven and baked a
one liter globe at 350C for an hour. Filled it with 15 torr of xenon.

Observations.

The new globe is super easy to start using the static trick.

The lower pressure globe uses less power. Still not low as some others have noted but I will not
say that my drive circuit is well tuned.

The ring in the lower pressure globe is not stable. It "attaches" itself to the coil and rolls around.

huxmans observation that the winding direction of the output coil is important is true. If I flip my
coil I can't get anything. It is pure luck that I got the right "polarity".

This is exactly the kind of observation that I was hoping for when I started this thread.

THEORY / HYPOTHESIS
From everything I have seen, the Theory involved acts similar to a standard transformer, in the way that most of these Tesla Coil builders make a primary and secondary,
But, in my hypothesis, and as the observations of others, the Magnetic field has a far greater effect than the voltage, or current moving through the coils.

In this case, the magnetic field is acting as a containment for the plasma inside the globe.
It also from what I can tell, when oscillating at the resonant frequency of the plasma, keeps the actual plasma reaction going and stable.

From what I can tell this is why when the voltage is adjusted, the oscillating frequency, between the coils and plasma changes.

From what I have read, regarding Zero-Volt Switching, when the CLASS E Oscillator circuit, is fine-tuned, there is only a small amount of voltage, but the circuit, OSCILATES in tune with the secondary in this case the plasma.

[sky-guided]

So a few minor facts to add to the information pile.

Background, I have an old xenon globe at 50 torr that I filled long before any toroid frenzy. It
makes a good but hot toroid display.

I ordered a few more globes and filled them with 15 torr and then 50 torr xenon. No toroid
behavior. I began to wonder if baking was the difference. So I build a sketchy oven and baked a
one liter globe at 350C for an hour. Filled it with 15 torr of xenon.

Observations.

The new globe is super easy to start using the static trick.

The lower pressure globe uses less power. Still not low as some others have noted but I will not
say that my drive circuit is well tuned.

The ring in the lower pressure globe is not stable. It "attaches" itself to the coil and rolls around.

huxmans observation that the winding direction of the output coil is important is true. If I flip my
coil I can't get anything. It is pure luck that I got the right "polarity".

This is exactly the kind of observation that I was hoping for when I started this thread.

THEORY / HYPOTHESIS
From everything I have seen, the Theory involved acts similar to a standard transformer, in the way that most of these Tesla Coil builders make a primary and secondary,
But, in my hypothesis, and as the observations of others, the Magnetic field has a far greater effect than the voltage, or current moving through the coils.

In this case, the magnetic field is acting as a containment for the plasma inside the globe.
It also from what I can tell, when oscillating at the resonant frequency of the plasma, keeps the actual plasma reaction going and stable.

From what I can tell this is why when the voltage is adjusted, the oscillating frequency, between the coils and plasma changes.

From what I have read, regarding Zero-Volt Switching, when the CLASS E Oscillator circuit, is fine-tuned, there is only a small amount of voltage, but the circuit, OSCILATES in tune with the secondary in this case the plasma.

With these self-oscillating "Class E" drivers, frequency doesn't much change when drive power is changed. The oscillating frequency is determined by the resonance of the LC circuit, given as

Code: [Select]

f₀ = 1 / (2pi * √(LC) ) It does make a bit of a difference whether the toroid is currently arcing (and where its floating) since that has some effects on the coil's inductance, but it's not the kind of feedback you suggest. The magnetic field is a consequence of the moving charges in the coil. And to be clear there's no "plasma reaction" -- the xenon isn't fundamentally changed in any way; it's a very similar phenomenon to the traveling arc of a jacob's ladder  where the already-ionized air is a path of lower resistance for subsequent arcing.

I'm fairly sure that this specific topology of self-oscillating drivers isn't at all required for the toroid effect; they're just convenient to make and don't require fiddly manual tuning. (Compare: the popularity of the "slayer exciter" and "mazzilli driver" high voltage sources.) I also feel like "Class E" is a bit of a misnomer here.

If one were to seriously study what's going on here in terms of plasma physics, the correct approach would probably be some combination of finite element analysis and actually waving around a field strength meter. Or even better, actually reading the original research papers that BacMacSci cited.

As a potentially more approachable experiment, I'd love to see what'd happen with drive frequencies outside of the now-customary 10-15MHz range.

[alan sailer]

sky-guided,

I agree about the frequency "stability". I have not spent lots of time watching the frequency vs bias. But when I did the frequency
did not vary (to first order) with bias change. And as I understand (which is very basic) the resonant frequency is the LC time constant.

I tried winding another coil more like huxman, with the high voltage (kV) junction of the LC on the bottom. It did not seem to make
the toroid more stable but I was shocked at one bias point when the toroid just spontaneously popped up. No start action required. It makes
a cute squeal and then starts it's wandering ways.

/>
This is one weird little interacting mess of electromagnetic effects.

Cheers.

[davekni]

I ordered a few more globes and filled them with 15 torr and then 50 torr xenon. No toroid
behavior. I began to wonder if baking was the difference. So I build a sketchy oven and baked a
one liter globe at 350C for an hour. Filled it with 15 torr of xenon.

Baking under vacuum is the ideal glass surface degassing process.  Neon sign makers use a process they call "bombarding".  It's not quite full vacuum because 2-3 torr of added gas is needed to pass high current through the tube to cause the heating.  Not clear if the hot plasma inside helps degassing or hurts it.

But, in my hypothesis, and as the observations of others, the Magnetic field has a far greater effect than the voltage, or current moving through the coils.

As a potentially more approachable experiment, I'd love to see what'd happen with drive frequencies outside of the now-customary 10-15MHz range.

A relatively high electric field is needed to start internal xenon glow discharge.  A lower field and higher current maintains the discharge (torus).  The starting electric field is usually capacitively coupled to xenon through tube wall, from a starting wand or from coil voltage.  Sustaining electric field is almost all induced by the AC magnetic field, which is why the discharge is a torus.  Not clear if the magnetically-induced electric field is ever high enough alone to start discharge.  That's something I hope to experiment with some day, using a single-turn coil (high current at relatively low voltage) to minimize capacitively coupled electric field.
Frequency will be a great variable for experimenting.  Lower frequency will require more current (stronger magnetic field) to induce the same electric field.  That stronger magnetic field should push the torus farther from coil due to stronger magnetic repulsion.  Farther from coil will reduce electric field.  May result in more self-extinguishing and restarting.  I expect high frequency will be most efficient at generating a stable torus close to coil.
Of course, buoyancy of of the hot torus also causes it to rise.  One of the videos shows the significant behavior difference between coil on top vs bottom of xenon-filled glass sphere.  With coil on top, torus is stable and closer to coil.  Don't recall which video shows this.

[OmGigaTron]

I finally ordered parts this week.
I have been working with Tate, (BackMacSci) and finally got everything ironed out.

Here is the circuit that I will be attempting to build:
https://www.circuit-diagram.org/circuits/24ddc75d2c05422cb0dfbe5f598448c6

Parts List:
https://www.digikey.com/en/mylists/list/6DCYSXEZJK
Total cost per unit is ~20$
I ordered some magnet wire, and I will have to wind the secondary to tune the circuit, but everything else is on that list if anyone wants to replicate this build.



I also pulled out a few of my EE Theory books, and have been reading them.

Sorry about being so quiet lately, Real life has been pretty busy.
But hopefully, I will be able to add some actual updates and contribute a bit more to this build with some real measurements.

I hope everyone has a most excellent week.
-Max

[Michelle_]

Check out what I found, there are mini plasma toroid generators and gas globes on aliexpress now:

https://www.aliexpress.us/item/3256806678903018.html?spm=a2g0o.store_pc_home.0.0.5f617d84Qz3GxW&gps-id=pcStoreNewArrivals&scm=1007.23409.271287.0&scm_id=1007.23409.271287.0&scm-url=1007.23409.271287.0&pvid=6decdcb1-6444-48cb-974b-92feb59ace40&_t=gps-id%3ApcStoreNewArrivals%2Cscm-url%3A1007.23409.271287.0%2Cpvid%3A6decdcb1-6444-48cb-974b-92feb59ace40%2Ctpp_buckets%3A668%232846%238108%231977&pdp_npi=4%40dis%21USD%2165.39%2165.39%21%21%21470.06%21470.06%21%402103297417151892807003769e32cb%2112000038817558759%21rec%21US%211653574204%21&gatewayAdapt=glo2usa

https://www.aliexpress.us/item/3256806669523156.html?spm=a2g0o.detail.pcDetailTopMoreOtherSeller.4.ec63H3YtH3YtEv&gps-id=pcDetailTopMoreOtherSeller&scm=1007.40050.354490.0&scm_id=1007.40050.354490.0&scm-url=1007.40050.354490.0&pvid=9709064f-d643-43e5-8869-5c45b5219357&_t=gps-id:pcDetailTopMoreOtherSeller,scm-url:1007.40050.354490.0,pvid:9709064f-d643-43e5-8869-5c45b5219357,tpp_buckets:668%232846%238108%231977&pdp_npi=4%40dis%21USD%2185.13%2185.13%21%21%21612.00%21612.00%21%402101e7f617151892895093313ecccc%2112000038526756379%21rec%21US%211653574204%21&utparam-url=scene%3ApcDetailTopMoreOtherSeller%7Cquery_from%3A

[Lasr8]

This is a great thread, happy that I've found it! Im very interested in trying to figure this circuit out and build one. Already this is some great info on the topic. I've purchased one of the xenon globes and now I'm trying to get the other components together, looking forward to this journey with yall.

[alan sailer]

A quick note. As huxman observed in their excellent video, grounding is very important variable in this
rather temperamental circuit. I had a good self starting circuit on a 15 torr glass globe that stopped
self starting. The ground lead had slipped from the heat-sink.

Another note is that this darn thing always seems to be operating on the edge of reliability. Changing
even apparently insignificant things can take you out of the realm of operation.

Good luck!

Cheers.

[OmGigaTron]

I started this project with a fire of motivation,
Sorry that I have not updated in a while,

I finally have all the parts and this weekend. I solved the heat sink issue.
I will be working on assembly and prototyping the physical layout soon, and after reading about so much work here done with High Voltage busses,
And especially Alan talking about grounding, I want to get this part right, and reliable.

Once I get a few pictures of the setup I will update with more.
I am still quite excited to work on this project, even if I work at a turtle pace compared to most others.