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Audio Modulated Tesla Coil


This Tesla coil was designed to play music. Plain and simple. Originally I wanted the best sound quality possible from an analog source, and at the same time the largest streamers possible. This lead to a long research phase where I tried to find out what could give this combination with the least effort. Several months passed with this project bouncing between ideas and nothing happening, until a friend suggested I use MIDI to interface with the Tesla coil. This is used in DRSSTCs and definitely gives the biggest sparks, since the coil is run at full power and the pulse repetition frequency is just varied (see my Polyphonic MIDI Tesla Coil Interrupter project). The disadvantage is that only square waves can be reproduced by the Tesla coil when using this type of audio modulation. However I was already using Steve Conner's PLL driver at this point, which has analog audio modulation implemented! Since one wouldn't affect the other, this driver has both analog and gated modulation.

PLL SSTC 2 schematic

The driver itself is pretty much identical to the PLL SSTC 1 driver, which is to say Steve Conner's PLL from his DWSSTC project. The additions I made for this particular SSTC were to include an inverter for the interrupter signal, so a high signal from the interrupter can either turn the coil ON or OFF. This is used so the MIDI interrupter can play music the "conventional" way so there are no streamers during silence, or so the coil can remain in CW mode with a interrupter signal, and thus play music via frequency shifting (analog). I purchased some UC3710T gate driver chips on ebay, which come in a nice TO-220 package, much easier to keep cool than dinky DIP8 gate drivers. Other than that there's not much new to anyone familiar with this driver. I've made a PCB for the driver, but unless you also acquire some UC3710T's it's not of much use. SSTC driver

Some specs on the coil for those who are interested. This one draws 1kW of power when run in CW mode, and the discharge is only 12cm tall or so. About the same size as the topload, which btw, is two steel Ikea bowls. They come in small, medium, and large, which is perfect for Tesla coiling although it would be better if they weren't completely spherical. The reason the discharge is so small for the coil size, is because I designed the coil to be run continuously while audio modulated, and also provide decent audio quality. This required the rather high drive frequency of 625kHz, and not much power throughput or the IRFP450s would overheat. As is, the only thing limiting the run time is secondary temperature, as the electronics stay cool. A pleasant change from my other High voltage projects, but in the end I wish there was some more bang.

Demonstration with MIDI Interrupter

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Disclaimer: I do not take responsibility for any injury, death, hurt ego, or other forms of personal damage which may result from recreating these experiments. Projects are merely presented as a source of inspiration, and should only be conducted by responsible individuals, or under the supervision of responsible individuals. It is your own life, so proceed at your own risk! All projects are for noncommercial use only.

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