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Plasma Ball

Construction
Circuit
Colors.

    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 extremely 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 gasses would drive the cost up more (want to buy one? just give me a few weeks and specify the gasses 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.
    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) from fully rectified wall voltage.

   

Above is a complete working system, below is a closeup of my bridge rectifier, and step down transformer (former transformer, they have a tendancy to burn out, as I have a tendancy to draw to much current from them, since this picture was taken, I have installed a 2 amp fuse, and reduced the number of transistors, and run it off the center tap ground instead of the other secondary (see the black wire).  This gives me 12.6 volts, which is a kind of wussy output for on my huge globe, the plasma is lousy with my less than ideal gasses, and all pictures on this page unless otherwise specified were taken with my overstressed transformer).  I tried increasing the resistance of the 220 ohm resistor, which in theorey will forces more current through the transistor (and the primary coil) improving plasma quality, while drawing no more current, but it didn't seem to change much really.

And here are my hand wound primaries!  I have since encased them in epoxy soon to increase efficiency, and prevent ever so commmon shorts.

And here is an arc generated by the power supply to a ground wire (I apologize for the poor image quality, small arcs in dark rooms are hard to photograph, but just for reference that arc is over a 1 inch gap!).

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 new complete system without the enclosure (I have mead experimental enclosures, but right now I am concentrating on my TC project, so the plasma globe will have to wait.)

The air is sucked out of the globe by means of a vacuum pump that in it's past life was an air conditioning compressor.

    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).  Also the freezer compressor spits oil all over the place, which I have corrected partially by covering the air out with a toilet float with holes in it.

     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 somthing I have a hard time doing with my larger globed prototypes. 

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.

These are some new pictures of my new flyback supply with a professional globe containing neon and xenon running at 300 mA 12V input into my flyback.

      The two images on the left show the plasma safely and painlessly grounded to my finger, the other two images are just free flying plasma, the display is very frantic with my professional globe and my most powerful transistor (I will have the part number soon).  At a much higher voltage and current with my new dc input, the entire globe fills with a colorful cloud of frantic streamers, unfortunately being a small globe the heat from my pumped up supply expanded the gas inside and cracked the glass so it is dead now (someday, I will stop crying over the loss, but at the same time woo-doggy, that is one tough little flyback!).  I have experimented with other transistors, and found the jitteryness goes away if you use a slower one, but some give poor results (like three streamers, that crawl slowly along) but two transistors I ripped out of TV's gave me virtually identical results to the original power supply with 300mA input, except the streamers twisted and bent which was kind of cool, and they were ultra quiet, the fast one made a high pitch scream which has got to kill every dog for miles.  Unfortunately, my transistors started dieing (including my fast one), they just couldn't handle the amperage without a heat sink, but I got about thirty MJ15015, and I put four in parallel.  I installed diodes to theoretically protect them from feed back induced from the high voltage spike, which may have helped.  The MJ15015 is nice because it is quiet, but it seems a little to delicate, for one thing, you must use several in parallel to keep them from frying, and they get so hot so fast, that their frequency changes, completely altering the characteristics of your plasma (which is inconsistent at best anyway).  I now use the famous 2N3055, which is the standby for hobbyists because it is reasonably powerful, and ultra cheap (for the price I paid for my original fast transistor, I could have bought 7 3055's.  The 2N3055 doesn't get hot to quickly (but you still need a heat sink) and it is more powerful than the MJ15015, the drawback is, usually it is silent with a frequency to high to hear, but unlike the MJ, a grounded arc does make some audible noise (My parents can't hear it, but my sisters and I can). 
     If you would like to build a plasma ball and cannot find a clear globe, I have found glass globes with a frosted finish, and it is possible to make them fairly clear by grinding and buffing, I tried to fire polish them which would have been ideal, but the things shattered from the stress, and I have had tragic accidents while trying to buff the things, so it is possible but not recommended as it is very time consuming and difficult, and one mistake means you must start over.  However covering it with a fluid of the same optical properties as glass makes the fine etching invisible, I have tried polyurethane and it works okay, but is far from ideal, you could use this if you had no other alternative.  My clear coat epoxy stuff works very well for this. 
     If however, you absolutely cannot find the necessary materials (or are just to lazy to construct a globe) you can use a large light bulb, it will work fine (but you will probably get zapped touching it, a bigger bulb is safer, but harder to find, also note, not every light bulb will work, they must have gas in them to work and generally the higher wattage ones work better, but steer clear of bulbs marked "new extra long life", I have tried one and it works poorly).  Here is a picture.

I now have a complete assembly.  I will 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).

    

    

    

    

    

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 brighterand more intense it is than the pictures above.

    

    

    

    

     These are my final working system, both free and painlessly grounded to my finger.  However, if ones finger is wet, you are in bare feet, and standing on a wet concrete floor, it will zap you in the soft area between the joints of your fingers, but you can't expect it to be perfect can you?  I seriousness though, if you touch it, make sure you are not grounded to any metal, and keep any metal from touching the globe, this makes the arcs hot and painful, and note also, a higher pressure carries more current than a lower pressure, so some of the cooler looking discharges with more light are less safe to touch.

     As said above, changing the pressure can drasticly change the characteristics of a globe, below are pictures of how my globe looked during an experiment (I don't intend to keep it this way, because it hurts 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, 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 acedic acid and CO2 leaking in from my silicone, I have never replicated the results seen here.

    


    

This is a long video of a non evacuated globe prototype of air contaminated argon.
Plasma video 1

This is a short video of an evacuated globe of air contaminated argon.

Plasma video 2

This is a short video of an evacuated globe of air contaminated argon grounded to one spot.
Plasma video 3

Here are some new videos with my flyback supply, the first is my professional globe containing neon and xenon at low pressure (note the jitteryness), the second is the same but on night vision (green is cool), and the third is simply the supply making tiny arcs (not much to look at, but I made it, and it works, so it makes me happy!  Now that I have 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 with all that fancy stuff, but it is very difficult to see.)  Next I have a video of a light bulb plasma ball (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.)  Following that 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!  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, then night vision, then a fluorescent tube being lit by RF emitted, and then finally my new supply video.  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

  Plasma video 4

Plasma video 5

Supply video

Light bulb plasma ball

Argon movie 1

Argon movie 2 (grounded)

Final system Prototype1

Final system Prototype2

Final system Prototype3

Fluorescent light

New supply

Final system light

Final system dark

High pressure argon

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Scott Bogard. 2007