The Plasma Globe:
I have for some time been endeavoring to build a homemade plasma ball (also called a plasma sphere, plasma globe, lightning ball and others, but regardless, it's technical name is an inert gas discharge tube), which is a high voltage discharge display contained within a glass sphere. The sphere is usually filled with low pressure noble gases, and the colorful arcs within the "ball" are attracted to one's finger as it is a direct path to the ground. You cannot be "shocked" by these because they have extremely low current, so they are safe to touch, and the frequency is high enough that even with higher current you still cannot feel a shock with the slow human nervous system. You have probably seen these before in Radio Shack or novelty stores, even Walmart. To build one might not seem worth the effort to most, but if you do it correctly you can have a beautiful (Big) display for a few bucks (mine has ended up costing me quite a bit, but now that I know how and have all the supplies (vacuum pumps, gases, etc.) I could spit out another complete working assembly for less than 95 dollars, expensive gases would drive the cost up more (want to buy one? just give me a few weeks and specify the gases you want, and we'll talk)). Plus the reward for building something by one self will always feel better than "just buying one", and yours is guaranteed to be unique, unlike the thousands of identical ones lining store shelves.
Principals of Operation:
So how do they work? Well, lets think about molecules shall we, inside the globe there are molecules of gas. When we apply a high voltage current, the electrons in the outer shell of the molecules jump to a higher energy shell. But they do not want to stay there, in that higher energy state, because atoms and molecules are lazy, so he jumps back down where he belongs. In order to do that, he has to get rid of the energy, and he does that by emitting a photon. So if we want to see some color, we must get high voltage. It must be also be AC electricity, other wise the electrons will shift orbitals and just stay there. I observed this effect once with a rectified transformer, it looked like an aurora, only very dim, and trapped in a tiny globe. AC is better, it gives you streamers. Below is how you get your high voltage AC.
The Circuit:
The circuit is basically a solid state Tesla coil which is actually a fudged flyback transformer from a television set. The schematic I used is shown below. The technical name is a Hartley Oscillator configuration of a Line OutPut Transformer (flyback).
The Rarefied Globe:
So we have high voltage AC, I bet if you turn it on, you won't see much color. No I didn't lie to you, I just left out the globe. We would need really high voltage to ionize atmospheric pressure air, that is what a Tesla coil does. We have a flyback transformer, it is not nearly powerful enough, so we need to make it's job easier. We do this by creating a low pressure environment, this makes the voltage more effective at ionizing the gas. I am going to put up pictures of globes at various pressures, as soon as I take them!
So how do they work? Well, lets think about molecules shall we, inside the globe there are molecules of gas. When we apply a high voltage current, the electrons in the outer shell of the molecules jump to a higher energy shell. But they do not want to stay there, in that higher energy state, because atoms and molecules are lazy, so he jumps back down where he belongs. In order to do that, he has to get rid of the energy, and he does that by emitting a photon. So if we want to see some color, we must get high voltage. It must be also be AC electricity, other wise the electrons will shift orbitals and just stay there. I observed this effect once with a rectified transformer, it looked like an aurora, only very dim, and trapped in a tiny globe. AC is better, it gives you streamers. Below is how you get your high voltage AC.
The Circuit:
The circuit is basically a solid state Tesla coil which is actually a fudged flyback transformer from a television set. The schematic I used is shown below. The technical name is a Hartley Oscillator configuration of a Line OutPut Transformer (flyback).
The Rarefied Globe:
So we have high voltage AC, I bet if you turn it on, you won't see much color. No I didn't lie to you, I just left out the globe. We would need really high voltage to ionize atmospheric pressure air, that is what a Tesla coil does. We have a flyback transformer, it is not nearly powerful enough, so we need to make it's job easier. We do this by creating a low pressure environment, this makes the voltage more effective at ionizing the gas. I am going to put up pictures of globes at various pressures, as soon as I take them!
Sounds
easy, doesn't it:
It is not that easy, ok, it is easy, but it is very difficult to make one that lasts a long time. Professional globe builders do things this way, get a globe (all pyrex glass) weld a glass discharge terminal inside (all glass again), then weld a glass fill tube to the bottom. Next they clean the globe in a solvent to remove all stuff inside and out. Bake the globe under vacuum in an oven for a few hours, remove it, fill it with argon, run it on high power for a few more hours, let the argon back out and now it is ready to be filled with the gases you want and then sealed. Why go through such fuss? because the glass will do something called out gas, it will let tiny air molecules stuck in the glass into your display over time. This will ruin the plasma effect. So, if you are thinking this is an insurmountable task for the average joe (who is not a glass blower), you are wrong, it is possible, just not cheap. you can purchas complete globes with no gass, if you can find them (they are rare, I cannot find them). If you have to build your own globe (like I do) then your life is harder, as you cannot simply put it into the oven for a while to treat it (it will melt your epoxy). To date, I have still not got a globe that I am completely satisfied with, but I have learned a lot on the way about their proper construction, and I think I have everything figured out now. More on that on my construction page, for now, enjoy the prototypes.
Vacuum Pumps:
Since we need a vacuum we need a vacuum pump, this is easy enough to come by cheaply. The cylindrical compressor on the left is from an air conditioner, the other one is from a freezer. The AC compressor gets the pressure much lower than the freezer, but it is slightly more complicated to wire (it has an external capacitor, whereas the freezer has an internal one). It is a rotary pump. The freezer compressor, which is a piston pump, spits oil all over the place, which I have corrected partially by covering the air out with a toilet float with holes in it.
Prototypes I and II:
Tragically my original globe was smashed by my discharge terminal when I evacuated it before allowing the silicone in my mount to completely dry (do not rush or you will pay for it later). But here is a picture of my second and current system without the enclosure (I have made experimental enclosures, but right now I am concentrating on my TC project, so the plasma globe will have to wait.)
Old Pictures of Operation:
Here are some pictures and videos of my prototype plasma balls in action, they are at various stages of development, the first 7 are my original (before I smashed it) globe powered by my Tesla coil which is way to strong for normal (quiet and safe) viewing, but for development reasons it worked just fine on low power. The next few are a professionally evacuated globe which I purchased at radio shack, being powered by my new UNRECTIFIED flyback supply (which is quiet and safe to touch). Now that I have finally gotten a new globe, a gargantuan 12 in diameter, I have made and entire system on my own. I will probably use wood or plastic for the enclosure. These pictures are last, under power of both my Tesla coil and my flyback oscillator. Please note, I still have not found a way to seal it forever, but I will have time to work on it whilst here at school.
The first images are Tesla coil based with my original now smashed
globe, the construction of which consisted of a 7-in glass tinted
globe, seated in
a flexible PVC pipe cap, with aquarium tubing for air in and out, and a
glass test tube to contain my discharge terminal, which was copper
scrub pad. The globe was sealed with RTV Silicone (this design
would
have worked okay with better inlet tubing,
but on a larger globe, it flexed to much from the vacuum making it not
ideal for my new system, not to mention the silicone was very difficult
to get to seal properly, but it did look cool with the copper
scrubby in the tube). Number one is of a non evacuated globe of
mostly argon
in
night
vision,
the second is an evacuated arc grounded to a wire, normally one could
touch the globe to induce the same effect, but at this pressure (just
slightly to high) and without throwing my coil way out of tune, I could
not touch it safely. When I really de-tuned my coil, I could
touch
it, but
I took no pictures of it in this state, and since my globe was smashed,
I can't make more. The arcs were somewhat dimmer and fuzzy, but
moved slower which is good, and were still visible enough to see with
the lights on (progress, yes!). You can see my blazing spark gap
and a capacitor on the left, my secondary coil is directly behind (see
the vertical glare?) as well as a hamster tube which I used to keep
voltage from leaking from my wire to the metal freezer it sat upon
(primitive I know, but I used what was there at the time!). This
globe if filled with mostly argon, of unknown purity.
The right most image is a non grounded image, where arcs are free
to
roam, they are rather frantic due to my coils high frequency (around
500 kHz), and less
than ideal pressure and gas mix, but they were a cool color, and had
the classic many streamered plasma globe look, which is something I
have
a hard time doing with my larger globed prototypes (I blame the bare
conductor and possible the frequency; it could even be a property of
argon gas for all I know).
Now I use
low pressure pure argon which gives me a bright
intense pink color streamers at the terminal (which is not covered with
glass anymore), which fade to lavender and
then to blue at the glass. There are a multitude of gases used
in
making plasma balls, And I shall list a few here
on my plasma color page.
Some of the
pictures are my own, some belong to other people, I have given them
credit when they are not mine.
The two
images on top show the plasma safely and painlessly grounded to my
finger, the bottom two images are just free flying plasma, the display
is very frantic with my professional globe and my most powerful
transistor (I believe it was a KSE13009, but since it
burned
out and I threw it away I cannot remember for sure). At a
much higher current with my new dc input, the entire globe filled with
a colorful cloud of frantic streamers, unfortunately being a small
globe the heat from my pumped up
supply ) cracked the glass so it is
dead now (it must have been arcing in there.
Someday, I will stop crying over
the loss, but at the same time woo-doggy, that is one tough little
flyback!).
It is not that easy, ok, it is easy, but it is very difficult to make one that lasts a long time. Professional globe builders do things this way, get a globe (all pyrex glass) weld a glass discharge terminal inside (all glass again), then weld a glass fill tube to the bottom. Next they clean the globe in a solvent to remove all stuff inside and out. Bake the globe under vacuum in an oven for a few hours, remove it, fill it with argon, run it on high power for a few more hours, let the argon back out and now it is ready to be filled with the gases you want and then sealed. Why go through such fuss? because the glass will do something called out gas, it will let tiny air molecules stuck in the glass into your display over time. This will ruin the plasma effect. So, if you are thinking this is an insurmountable task for the average joe (who is not a glass blower), you are wrong, it is possible, just not cheap. you can purchas complete globes with no gass, if you can find them (they are rare, I cannot find them). If you have to build your own globe (like I do) then your life is harder, as you cannot simply put it into the oven for a while to treat it (it will melt your epoxy). To date, I have still not got a globe that I am completely satisfied with, but I have learned a lot on the way about their proper construction, and I think I have everything figured out now. More on that on my construction page, for now, enjoy the prototypes.
Vacuum Pumps:
Since we need a vacuum we need a vacuum pump, this is easy enough to come by cheaply. The cylindrical compressor on the left is from an air conditioner, the other one is from a freezer. The AC compressor gets the pressure much lower than the freezer, but it is slightly more complicated to wire (it has an external capacitor, whereas the freezer has an internal one). It is a rotary pump. The freezer compressor, which is a piston pump, spits oil all over the place, which I have corrected partially by covering the air out with a toilet float with holes in it.
Prototypes I and II:
Tragically my original globe was smashed by my discharge terminal when I evacuated it before allowing the silicone in my mount to completely dry (do not rush or you will pay for it later). But here is a picture of my second and current system without the enclosure (I have made experimental enclosures, but right now I am concentrating on my TC project, so the plasma globe will have to wait.)
Old Pictures of Operation:
Here are some pictures and videos of my prototype plasma balls in action, they are at various stages of development, the first 7 are my original (before I smashed it) globe powered by my Tesla coil which is way to strong for normal (quiet and safe) viewing, but for development reasons it worked just fine on low power. The next few are a professionally evacuated globe which I purchased at radio shack, being powered by my new UNRECTIFIED flyback supply (which is quiet and safe to touch). Now that I have finally gotten a new globe, a gargantuan 12 in diameter, I have made and entire system on my own. I will probably use wood or plastic for the enclosure. These pictures are last, under power of both my Tesla coil and my flyback oscillator. Please note, I still have not found a way to seal it forever, but I will have time to work on it whilst here at school.
These are
some pictures of my flyback supply with a
professional
globe containing neon and xenon running at 300 mA 12V input.
Newer
Pictures
of Operation:
I now have an assembly that works well enough to experiment with different types of gases at different pressures. Here are some pictures
I now have an assembly that works well enough to experiment with different types of gases at different pressures. Here are some pictures
These are
pure air globes powered by my Tesla coil. Below is
a
prototype
of the final system, the primary gas is Argon, although it is
contaminated (note the dimness of the streamers, and fuzziness, this is
from air, I developed a system of charging that gets all the air out,
but it uses a lot of argon). The left images are taken with night
vision, and are similar in apperance to the right images.
Here (unless I
save up enough for neon, krypton, and xenon
gas) is how I am going to leave my system, it is as
pure argon as I can get, notice how much brighter and more intense it
is
than the
pictures above. These are
my current and best working system, both free and painlessly grounded
to
my finger.
High
Pressure Pictures
of Operation:
As said above, changing the pressure can drastically change the characteristics of a globe, below are pictures of how my globe looked during an experiment (I couldn't keep it this way, because it hurt to touch it) of an almost atmospheric pressure discharge, a very interesting fact, is that a covered discharge terminal actually raises the working pressure of a plasma display! One would be led to believe that no cover would mean less resistance and more power, but this is not true. I now believe that the thin insulating layer acts like a capacitor, somehow increasing transient current, so a higher pressure discharge is possible. Note in the pictures below, the non grounded arcs that do not touch the glass are actually very orange in color, but the grounded (slightly tingly) arcs are very white, almost blueish! I have a video at the bottom of the page. The interesting colors and raised pressure came from acetic acid and CO2 leaking in from my silicone, I have never replicated the results seen here. After the globe was contaminated, I added more argon until I could add no more, and this is what I got.
As said above, changing the pressure can drastically change the characteristics of a globe, below are pictures of how my globe looked during an experiment (I couldn't keep it this way, because it hurt to touch it) of an almost atmospheric pressure discharge, a very interesting fact, is that a covered discharge terminal actually raises the working pressure of a plasma display! One would be led to believe that no cover would mean less resistance and more power, but this is not true. I now believe that the thin insulating layer acts like a capacitor, somehow increasing transient current, so a higher pressure discharge is possible. Note in the pictures below, the non grounded arcs that do not touch the glass are actually very orange in color, but the grounded (slightly tingly) arcs are very white, almost blueish! I have a video at the bottom of the page. The interesting colors and raised pressure came from acetic acid and CO2 leaking in from my silicone, I have never replicated the results seen here. After the globe was contaminated, I added more argon until I could add no more, and this is what I got.
Videos
of
Operation:
This is a long video of a non
evacuated globe prototype I of air
contaminated argon.
This is a short video of an
evacuated globe I of air
contaminated argon.
This is a short video of an
evacuated globe I of
air contaminated argon grounded to one spot.
Here are some new videos with
my
flyback supply, this is my professional globe containing neon and
xenon at low pressure (note the
jitteryness).
This is the
same but on night vision (green is cool),
This is simply the
supply making
tiny arcs (not much to look at, but I made it, and it works, so it
makes me happy! When I run it on full power, with my 25 volt
transformer, it
discharges to the air like a tiny Tesla coil with half centimeter
long arcs, and an arc grounded to the high voltage return (the
equivalent of an RF ground, it is just a wire coming off the bottom of
the flyback) can be stretched out to an inch and a half, and looks like
the thick plasma streamer coming off my Jacobs' ladder!.
The new
supply video is configured full power, but it is very
difficult to see.
Here is a video of
a light bulb plasma
ball, please don't mind the audio commentaries, the supply was burning
up
when I made it, so my father and I had a hard time getting it to
work for the camera.
Here are two videos
of the
flyback in a pure argon atmosphere (recycled juice jug slowly filled
with cold atmospheric pressure argon), a real must see! Very cool.
The next
video is my final prototype, with
70/30 argon helium mix and pressure just slightly to high (it doesn't
really like my finger at
this pressure.)
Next is pure argon
(almost, traces of helium and
air), at a much lower pressure.
The same on night vision.
This is a
fluorescent
tube being lit by RF emitted.
The next two videos
are how I plan to leave my plasma
globe, one note however, the colors are not accurately depicted, the
camera is not sensitive to all the frequencies that the human eye is,
and the long grounded arcs have an orangish tint, which you cannot see
here. Another note, in some of the below videos, you can hear a
rumbling noise, this is not the power supply, this is the furnace, with
the right transistors, the only thing you can hear is the plasma itself
banging against the glass!
And finally the last
video is my high
pressure globe with a covered discharge terminal