Re: [TCML] Audio modulated coils: where to start?

["Curtis Cherry" <willworkforgas@xxxxxxxxxxx>]

   Pulse Width Modulation (PWM) is the method used to modulate the 
amplitude of power going into your coil.  Its what the plasmasonic uses 
which is polyphonic.  It works by varying the amount of time the switches 
(mosfets or igbts) are turned on compared to the off time.  DRSSTCs cannot 
operate in this mode to the best of my knowledge because they are a pulsed 
coil.

   PRF uses "bursts" that are all the same length of time.  A rapid 
succession of bursts renders a high frequency whilst a slow seccession 
yeilds a low frequency.  This type only does well with monophonic because if 
you mix two different frequencies you just get the sum of those frequencies 
which sounds "harsh".  I believe that the xenosonic board works in this 
manner.

   I too am copying Steve Wards "Mini SSTC" for my first coil except using 
quite a bit larger secondary.  I am using fibre optic cable with toslink 
ends to enable the gate drivers and my inturuppter will be a Basic Stamp 
with the PWM pal.  With the micro I will be able to vary the pulse rate and 
duty cycle to just about anything I want.  I picked the Basic Stamp because 
I already know basic (had a radio shack color computer)and it uses a a very 
close variant.  It will be fancy with backlit LCD, rotary encoders, 
swithches, LEDs etc.  I would like to use a more powerful micro but I want 
to be en expert coil builder before I learn assembly language for the more 
complex micros.

   I also kinda like the monphonic too, but I am gonna try to do both with 
my coil once it is built.  PWM uses a different type of controller but the 
bridge is the same to my coil is going to be completely modular.   i.e. 
Controller Board, Bridge, Power Supply all seperate in thier own enclosures 
connnected with appropriate connectors.

   Steve uses double sided boards with the top being the ground plane.  It 
lends itself to both high currents and good RF noise shielding.  I am 
building my bridge on double sided 3oz. per side boards but I build all my 
other circuits on 3 hole perfboard.  It looks like standard perf board but 
every 3 holes are on the same copper.  I am not good enough at soldering to 
build on standard perf board and "drag" the solder to make connections.  I 
also socket all ICs because come on, this is TC duty.

   Keep in touch and keep me update on your progress.  If only Tesla knew 
how he changed the world as well as gave us all the most interesting hobby 
in the world.!!!  Good Luck to all.


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