Re: "Singing Arc" Project

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Dan,
        There's two comments I'd make - you don't need the output 
buffer (I guess you're using the second half of a dual OA so what the 
heck). The second is, the source impedance will have to be low for 
the gain to be set accurately using that circuit.

Regards,
Malcolm

On 11 Sep 2002, at 21:11, Tesla list wrote:

> 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
> 
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