"Singing Arc" Project

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dhmccauley-at-spacecatlighting-dot-com>


Currently working on my singing arc project.  Here is my status so far:

http://www.spacecatlighting-dot-com/teslacoil6.htm    (webpage)

1.  Need to create a DC power supply.  Will use 115VAC mains, bridge
rectified with about 16000uF, 450V smoothing capacitor

2.  Singing Arc requires PWM modulation of my FET gate drivers for low-level
topology.  This will be accomplished by using my existing TL494 PWM
Controller IC on both my
SSTC#1 and SSTC#2 as seen at http://www.spacecatlighting-dot-com    To
accomplish this, the audio signal will need to be scaled and fed into my
TL494 Feedback (comparator) input which requires a 0.5VDC input for 95% duty
cycle and a 3.5VDC input for 0% duty cycle.  I will choose the midpoint (2
VDC) to be the bias point for my feedback input, or otherwise with no audio
input, the PWM controller will output approximately 50% duty cycle.

My audio source will be a broken DVD player (only reads DVD's about 50% of
time and CD's about 90% of time).  I will use the line-level audio output
which has maximum value of 2 Vrms operated into a 50k impedance (nominal
output impedance is 10k)  2 Vrms is about 5.6V peak-peak so this will need
to be scaled to a 3.0V peak-peak signal (0.5V to 3.5V duty cycle adjust
voltage as in last paragraph) centered about a 2V bias point.  The following
circuit illustrates my audio pre-amplifier:  Single-power supply rail is
used since that is currently the only available Vcc.

http://www.spacecatlighting-dot-com/audioscale01.pdf


If anyone has time, please look at my circuit and see if there is anything
you would change, add, or delete.  All comments appreciated.

Thanks

Dan