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Re: [TCML] Coil Conversion Project.
On 8/18/12 4:36 PM, Jim wrote:
Hello,
Five plus years ago the kind folks who frequent this website helped me
build a 30" arcing classic tesla coil. Can you please point me in the
right direction as to where I may obtain instructions on how to convert
this into a musical coil. I utilized the online Java design tool when
building the classic if anyone would like a copy of the specs.
Spark gap coil?
It's a lot trickier than for a SSTC.
The trick is to get variable numbers of sparks per second. The scheme
I've used (with middling success) is to use a triggered spark gap, with
the trigger signal driven by an oscillator controlled by your music.
I used an automobile transistor ignition to drive a conventional
ignition coil to generate the trigger pulses, and drove the ignition
from a 555, with some carefully chosen resistors to set the rates giving
me a grand total of 5 different notes. One could use a VCO scheme (Oh,
that I had built this back in the 70s.. I probably could have convinced
Keith Emerson to build a giant oneone on to his Moog.. how delightfully
prog rock)
Today, I'd drive it with an arduino or something similar that could take
a MIDI input. I think you could probably modify a HEI type ignition:
the magnetic pickup coil is replaced with an Optoisolator, or even
better, a optical receiver and some inexpensive 1mm plastic fiber optic
cable (TOSlink, e.g.).
The tricky part is that to make decent music, you need to run off DC, or
the 120 Hz power line buzz gets in the way (or 100 Hz). I suppose you
could have a restricted scale and choose notes that have "nice"
relationships with 120 Hz.
I have a big 10kW 30kV power supply running off three phase that I've
contemplated using.
To run any serious power, that DC supply, off single phase, is going to
take a terrifyingly large filter capacitor. (and I've worked with big
pulse power.. I have a healthy, healthy respect for things that store
kilojoules)
Another scheme which I've always wanted to try is to have a bunch of
rotary gaps, either running at different speeds or with different
numbers of electrodes, and switch between them. (Take that Hammond B3
tonewheel organ!).
Apparently someone DID build something like this about 100 years ago.
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