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Plans for a Mini 120V Tesla coil ( Science Demo style )

Discussion in 'High Voltage' started by DJDAudio, Jan 27, 2012.

  1. DJDAudio

    DJDAudio New Member

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    I have worked on so many of these things, I decided I would draw up the schematics and specs so others can build there own if interested, they are of a very unique design for a Tesla coil.

    [​IMG]

    This will build you one like this,

    [​IMG]

    :cool:

    they do not use a normal High voltage transformer on the primary as most are used too, they use what is referred to as an oscillator, think of it is a large solenoidal relay.

    From my best guess of the design, the High voltage back EMF pulse from the solenoid coil is used to charge up the caps, and when the contacts close the power is dumped into the primary.



    Any questions ask away.
     
  2. DJDAudio

    DJDAudio New Member

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    Here is one that I built,

    [​IMG]

    [​IMG]

    I will try to dig up the video but it will light up a florescent tube from 2 feet away!
     
  3. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Very interesting idea, but though it looks like a tesla coil, I don't believe it fits the definition. A Tesla coil relies on resonance of the coils to increase the voltage exponentially. I think what you have here is actually an air-cored induction transformer that uses a circuit interrupter that operates with mains frequency, which is more closely related to an ignition coil than a Tesla coil. I'm still very curious about it though. What kind of voltage output do you get? It is definitely a very clever idea, and I am tempted to give it a try myself. I've built many tesla coils before, but I have not ever built a transformer of this style. Also, what's the output frequency sound like? I imagine it has a 60 hertz hum, rather than the several hundred kilohertz that a classic tesla coil would emit.

    A video would be awesome! Thanks for posting!
    Regards,
    Der Strom
     
  4. dave

    Dave New Member

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  5. DJDAudio

    DJDAudio New Member

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    Will get a Video up very soon, the output arc will jump at 1.25" at STP

    As for tuned resonance, I do feel there is something to that with this coil, for the knob will adjust the contacts and there is a 'sweet' spot where the output will be the greatest.

    About the sound, the oscillator is so loud you can barely tell but I have some ideas on how to tell.

    Also given the 1.75:260 turns or 1:148 Ratio , if the input was 1,600 that would be an output of 236,800V So you may be correct on this! but then again the input may only be 120V or 17,760V at the output. if that was the case it would never make the 1.25" Jump

    Allot of Food for thought, you have me thinking now, and will look some more into this!
     
  6. DJDAudio

    DJDAudio New Member

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    Also the Sprague 'orange drop' capacitors they use are high frequency capacitors if that helps.
     
  7. DJDAudio

    DJDAudio New Member

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  8. JimW

    JimW Member

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    It is tough to tell from the schematic if it qualifies as a Tesla coil. I have several of them built similarly that are Tesla coils. They use an adjustable spark gap as the frequency adjust for the resonant frequency of the secondary wound coil. The easy way to tell if it qualifies as a Tesla coil is to make a moderate adjustment to the spark gap (and thus changing the frequency of oscillation). If the output discharge goes away, then it probably was running at the resonant frequency, and is a real Tesla coil.

    -Jim
     
  9. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Jim, there is no spark gap on this "tesla" coil. It is mainly just a standard circuit interrupter, and though you might be able to reach resonance with this one, it does not operate by it. I am about 90% sure this would not actually classify as a real tesla coil, but it is certainly a high voltage air cored transformer, and that in itself is very clever and fascinating. It does not need to be a real Tesla coil to be cool ;)
     
    Last edited: Jan 29, 2012
  10. DJDAudio

    DJDAudio New Member

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    Sorry this took so long, Ran up and got a Video for you guys. The 3' Tube was hand held and not grounded, or be it through me.



    so what are your thoughts?

    I will try to get a scope on it to see if it is high frequency soon.
     
    Last edited by a moderator: Sep 10, 2013
  11. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Well, that is an interesting specimen now, isn't it :D

    The output does indeed look like that of a tesla coil. However, I feel if it was a real Tesla coil, you'd be able to tune it to get streamers (to air) much longer than what you have. I really can't say for sure, though. I suppose you could call it a simple low voltage tesla coil, but it can't really be proved that it IS one without testing for resonance. Regardless of what it is called, you did a fine job DJ. It's a very interesting project indeed!
     
    Last edited: Jan 30, 2012
  12. JimW

    JimW Member

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    ***
    Jim, there is no spark gap on this "tesla" coil. It is mainly just a standard circuit interrupter, and though you might be able to reach resonance with this one, it does not operate by it. I am about 90% sure this would not actually classify as a real tesla coil, but it is certainly a high voltage air cored transformer, and that in itself is very clever and fascinating.
    ***

    But this is exactly where it is not clear. The solonoid operating as a buzzer to create the AC frequency has a screw adjusting knob. To me this is essentially an adjustable spark gap. Or at least it could be used as one. The farther the solonoid travel, the longer it would take to return, the lower the frequency. I have used the same technique to make different frequency buzzers. The concern I would have is that the frequency range would be fairly small. And designing a coil to resonate at that frequency would be problematic.

    As far as the picture goes, what happens if the fluorescent light is not present? Do you get the random streamers? Or is there no output until you provide the path to ground? I tend to agree with DerStrom, it is just a air core transformer. But with a bit of work...

    -Jim
     
  13. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    All a spark gap is is a switch. It does very little to change the overall frequency, unless you have a DC circuit, in which the air inside it would break down only when there is enough voltage across the capacitor. However, in AC the capacitor would discharge every half cycle of the mains supply. This, or course, is about a real Tesla coil, but I hope you get my point. The distance inside the spark gap does very little to change the frequency, and therefore has little effect on resonance. To tune a Tesla coil, one would have to change the value of the capacitor or the inductance in the primary coil. The spark gap should be set as wide as the spark will jump, and left there.

    I realize you're agreeing with me--I just wanted to clear this up :D

    Regards
     
  14. DJDAudio

    DJDAudio New Member

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    The output is directly affected by the adjustment knob and the frequency of its oscillation. I will try to get a video of what I am talking about.

    As for streamers, they are there if you kill all of the lights, but only become vibrant when a source to ground is close by.

    I love the way this discussion is going, lets keep it going.

    I have always been curious as to the operations of these 'coils' and you all now have me questioning if it is indeed a Tesla coil at all, Let me know what tests you would like me to conduct I will do my best as time allows.
     
  15. DJDAudio

    DJDAudio New Member

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    Also, I tried to double the wraps on the primary with a larger Gauge wire to maintain the same resistance. The effect was not double the output the opposite in fact almost no output at all. If this was an Air core Transformer I would image the output voltage would have gone up.

    Thoughts?
     
  16. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Two things: First, resistance isn't important. In a transformer, inductance is what is important. You lowered the resistance, but the inductance was still probably increased. Increasing the inductance on a regular transformer would lower the output voltage (lower ratio), but on a tesla coil it is very picky, and the inductance must be just right.
     
  17. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Interesting distinction you all make for what is a Tesla coil. In my days of doing high vacuum work, we used a "Tesla Coil" like this to test for pinhole leaks in our glass blowing:

    [​IMG]

    Everyone , including full, tenured professors, called it a Tesla coil. Now, it appears the same device is just a "high frequency generator" (http://www.electrotechnicproduct.com/pinhole.asp).

    The design of our/these HF generators was very similar to this design, so I suspect it really may not meet the strict definition of a Tesla coil.

    John

    PS: The knob on the back is for adjusting the oscillator resonance.
     
    Last edited: Feb 1, 2012
  18. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Yes, I have seen those before and they bug the cr@p out of me! They are simply high voltage transformers loosely based on the theory of a Tesla coil. I just can't believe how much people have twisted Tesla's designs and still called them Tesla coils! :eek:
     
  19. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Hey, the new Ford ain't nuttin like the original. It's reliable, quiet, fuel efficient, and has an electric starter. We still call it a Ford with pride, though. :)

    The question is whether Tesla defined his coil in such a way that would exclude these later derivatives? Clearly, the little tuning knob on the end makes quite a difference. Did Tesla ever patent his coil (I am not a student of Tesla)? If he did, that would be a good source to see how broadly he considered the concept.

    John

    Edit: Here's one of Tesla's patents: http://www.tfcbooks.com/patents/1119732.htm The fact that adjustment of the oscillator changes the output (the effect is quite noticeable when looking for pinholes) would seem to qualify it as a Tesla coil. I'll bet Tesla's attorneys would also agree -- at least while the patent was valid.
     
    Last edited: Feb 1, 2012
  20. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    I know of Tesla's coils, but what I don't know is how these newer ones are made. I would like to know what is inside that little black tube.

    I've been thinking about what I was saying, and realized that according to what I originally said, modern-day solid state tesla coils would not actually be Tesla coils. I guess what I am troubling over is where to draw the line. What actually classifies it as a Tesla coil? (I think that's just about what you said in your last post). Where does it go from being a true Tesla coil to an imitation high-voltage high-frequency transformer that is being passed off as a TC? I guess this calls for a little more research....
     
  21. DJDAudio

    DJDAudio New Member

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    [​IMG]

    I have that exact one here in the shop, and yes same exact internals as the schematic , and mine is listed on the side as a high frequency generator.
     

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