### Author Topic: What will allow me to maintain an arbitrary waveform through a tesla coil?  (Read 909 times)

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#### Centripetal heterodyning

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##### What will allow me to maintain an arbitrary waveform through a tesla coil?
« on: May 14, 2020, 04:09:40 am »
I've seen it possible that an arbitrary waveform ... Guess I should give you a shape

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--      ----                   ----     --
--      --                                --     --

Don't know why I drew it out like that. Here's a picture.

ANYHOW

I've seen an arbitrary waveform (vs a sine wave obviously) be used to create (somewhat best it can be) resonance and therefore high voltage. Whichhh, maintains this arbitrary waveform shape.. When I do it on a small scale, just to test things my arbitrary waveform ends up molding itself into a sine wave. This.. of course... makes sense.. but I'm not as good as you think guys. I hardly know why this makes sense. With a best guess I would say I need more power? The little bumps on the side of the spike of the form are so unpronounced that more power will be needed to combat the tesla coil smoothing effect? Does anyone know exactly maybe an equation that can show me this?
« Last Edit: May 14, 2020, 04:39:08 am by Centripetal heterodyning »

#### Centripetal heterodyning

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##### Re: Does anyone know much power to maintain an abribitrary shape in a tesla coil
« Reply #1 on: May 14, 2020, 04:18:41 am »

"When current flows in an inductor, energy is stored in the magnetic field surrounding the inductor. The magnetic field becomes an energy source that prevents abrupt changes in the current through the inductor. What would have been current pulses through the inductor gets smoothed by the action of the stored energy in the magnetic field.

An inductor in an electrical circuit is akin to a flywheel on a rotating shaft, preventing abrupt changes in the rotational velocity of the shaft."

Source: Gil Hoffman, Retired electronics engineer. - www.quora.com "How-do-inductors-smooth-the-output-current-of-a-rectifier"

#### Centripetal heterodyning

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##### Re: What will allow me to maintain an arbitrary waveform through a tesla coil?
« Reply #2 on: May 14, 2020, 04:56:29 am »
Found more, https://www.eevblog.com/forum/projects/square-wave-magnetic-field/

Sorry guys I'm dumb. Electronics are something I want to learn at a later age. And am stepping into this project only by following one step at a time. Does anyone know how I can produce the best copy of this waveform through a tesla coil secondary and still get high voltage

#### Berni

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##### Re: What will allow me to maintain an arbitrary waveform through a tesla coil?
« Reply #3 on: May 14, 2020, 05:25:29 am »
The very point of a Tesla coil is resonance between the big tall coil with the stray capacitance of the part on top.

So a Tesla coil is actually designed to turn whatever kicks of power shoved into its primary into a long drawn out smooth sinewave oscillation on the secondary. Its just a transformer with a very pronounced self resonant point combined with the very low loss from the air core.

If you want to put an arbitrary waveform trough then then you need a normal step up transformer that has a wide enough frequency response for whatever waveform you are trying to put trough it. It also likely requires a rather large amplifier to drive this waveform into the transformer.

The following users thanked this post: cdev, Centripetal heterodyning

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##### Re: What will allow me to maintain an arbitrary waveform through a tesla coil?
« Reply #4 on: May 14, 2020, 11:42:44 am »
The wave form you provided is nothing like the repeating damped oscillation produced by a Tesla coil. It looks like a Sin x / x curve. What is your source?
Glenn

#### cdev

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##### Re: What will allow me to maintain an arbitrary waveform through a tesla coil?
« Reply #5 on: May 14, 2020, 12:06:16 pm »
A Tesla coil is the low frequency equivalent of a laser. It really wants to "ring" like a bell at its resonant frequency.

Watch out, they can be dangerous.
"What the large print giveth, the small print taketh away."

#### Centripetal heterodyning

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##### Re: What will allow me to maintain an arbitrary waveform through a tesla coil?
« Reply #6 on: May 15, 2020, 01:34:54 am »
Not intending to make sparks. Actually interested in a large high voltage electric field.

@gbaddeley its not anything I measured. Well, it was something I measured from a tesla coil, but specifically it is an arbitrary wave from an equation. The source is a signal generator > tesla coil > and this is the output. I'm just trying to reproduce it and don't know how.

@Berni thanks that's what I thought. Sounds good to hear from others because it was just my basic guess LOL

#### Berni

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##### Re: What will allow me to maintain an arbitrary waveform through a tesla coil?
« Reply #7 on: May 15, 2020, 05:33:42 am »
If you are fine with 10s of kV you can make use of old TV flyback transformers that generate the CRT acceleration voltage. But you need to get the old ones without the built in rectifier, or carefully chip away at a modern one to tap off the secondary winding output directly. These typically work in the 10s to 100s of KHz

You can go to a few MHz with power ferrite cores, beyond that they will overheat from the terrible core losses. Here air core transformers might be the answer but careful design is needed to avoid resonance since all those stray picofarads are eagerly waiting to create a LC oscillator with the transformers inductance. This won't work in the KHz territory however

But if your signal bandwith is <10KHz then things get easier because you can start using laminated iron transformer cores (like the ones used in 50Hz mains transformers) and drive them with normal off the shelf audio amplifiers. But these will go down to Hertz if you can find a giant transformer core that is big enough.

#### Jwillis

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##### Re: What will allow me to maintain an arbitrary waveform through a tesla coil?
« Reply #8 on: May 15, 2020, 07:58:13 am »
Not intending to make sparks. Actually interested in a large high voltage electric field.

@gbaddeley its not anything I measured. Well, it was something I measured from a tesla coil, but specifically it is an arbitrary wave from an equation. The source is a signal generator > tesla coil > and this is the output. I'm just trying to reproduce it and don't know how.

@Berni thanks that's what I thought. Sounds good to hear from others because it was just my basic guess LOL

So basically you want to modulate the tesla coils wave. Think of the Musical group "ArcAttack" where they modulate the tesla coils high frequency wave to produce a tone . You can You tube ArcAttack to see what they do. Audible tones but not high-fidelity.  It's an interesting effect but you would lose your wave form in the high frequency carrier wave.
The coil rings like a bell every time the primary coil is charged. It's charged by discharging capacitors across a spark gap or a pulse from a transistor.
Now imagine  you attach a speaker to a bell. While the bell is stationary you can listen to you IPod over the speaker and the bell may even amplify it a bit. Now grab a sledge hammer and repeatedly bang the bell .

Smf