RE: Building A VTTC

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Cameron B. Prince" <cplists@xxxxxxxxxx>


Hey guys,

I think the consensus is we need some sort of counter to help determine the
current pulse rate of the staccato controller. John, this is what I had
emailed you about a few weeks ago. I think it would be really nice to
incorporate two 7 segment displays into the controller that display current
pulses per second. I have briefly looked into this and found the schematic
here:

http://martybugs.net/electronics/speedo.cgi

It's for a digital speedometer display but I think the concept is about the
same:

1) Take a sample
2) Perform an average
3) Display value
4) Return to step 1

What are your thoughts on this circuit and adapting it to interface with the
staccato controller? Is there a less complex way or circuit that would
provide the same results that you know of?

Thanks,
Cameron

> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Monday, August 21, 2006 6:58 PM
> To: tesla@xxxxxxxxxx
> Subject: Re: Building A VTTC
>
> Original poster: FutureT@xxxxxxx
>
> In a message dated 8/21/06 4:07:27 PM Eastern Daylight Time,
> tesla@xxxxxxxxxx writes:
>
> >It seems that you have made a quantum leap in
> >the stacatto controlled VTTC that probably hasn't been pa-
> >ralleled since the 1990s when John Freau himself first intro-
> >duced the stacatto controlled VTTC, capitalizing upon the
> >higher output from the same power input through the
> >priciple of lower duty cycle firing. And I also think that it
> >should be pointed out to the rest of the list that this is your
> >very first VTTC project, so basically you've made these
> >advances as a VTTC beginner!
> >
> >Keep up the good work,
> >David
>
>
> Cameron, David,
>
> Yes, Cameron has obtained very impressive results from his
> VTTC project.
>
> My original coil that gave the 36" sparks, and later
> the one that gave 38" sparks didn't have a staccato system
> attached, so they ran at 60 PPS, and drew a lot of power.
> These early designs were unable to give the straight sword-like
> sparks, so the sparks tended to get a lot shorter when the
> staccato feature was added.  I did at some point add the
> staccato feature but the sparks got shorter when the staccato
> was operating.
>
> One of my early coils gave the sword-like sparks.  In this
> coil the spark length did not decrease in the staccato mode.
> I could reduce the pulse rate to 1 pulse per minute, and the
> sparks remained just as long.  But this was a smaller coil
> which produced 20" sparks from a single 4-250A tube
>
> When I added the staccato system to my coils in general
> I didn't go back to modify the coils to take advantage of the
> staccato features, so the sparks didn't get any longer, the
> input power simply decreased.
>
> When I had spoken to
> Steve Ward and others, I suggested that they modify their coils
> (compared to mine) by lowering the plate impedance to take
> advantage of the staccato capabilities.  This is what I was planning
> to do but I got involved in other work.  Also around that time I had
> introduced the zero-crossing staccato circuit which helped a lot for
> staccato stability.  I sent this schematic to Steve Ward and he
> incorporated it into his coil and placed the schematic at his
> website.  He did optimize his coils to take advantage of the
> staccato, by lowering the plate impedance.  Cameron has
> done that also.
>
> Some later coils that I built did give the sword-like
> sparks, so they were able to maintain their spark lengths
> while running at a slower staccato pulse rate.  One later design
> coil (circa Feb, 2001) produced 24" swordlike sparks in the
> staccato mode and also without staccato.  This coil used two
> 833A tubes and was capable of running without staccato
> without overheating the tubes.  It produced 24" sparks.
> When running without staccato it drew 2400 watts while
> producing the 24" sparks.  By using the staccato, the
> power draw could be dramatically reduced depending
> on the pulse rate.  For example if the coil was run at 30 PPS,
> Then it drew 1200 watts (somewhere around 10amps).  If the
> coil was run at 15 PPS, then it drew 600 watts (~ 5 amps).
>
> I use a similar formula to my formula for spark gap coils,
> for VTTC's without staccato.
>
>       spark length inches = 0.5*sqrt input watts.
>
> This formula is for VTTC's which are running at the full 60 PPS
> (no staccato).  The coils will of course be much more "efficient"
> in staccato mode.
>
> As an example there is my 2nd large VTTC coil which gave the
> 36" sparks at around 5500 watts.  So if we take the sqrt of
> 5500 = 74.16.  Then multiplying this by 0.5 gives 37" which is
> very close to the 36" I obtained.  I think I turned up the power
> a little higher to get the 38" which I eventually obtained.
>
> Now we can do an example with staccato mode.  Consider
> my coil that gave 24" sparks both in or out of staccato mode.
>
> without staccato:
>
>     24.49" spark length = 0.5*sqrt 2400 watts
>
> So it can be seen the formula is quite accurate for this coil also.
>
>    But with staccato at 20 PPS the formula must be modified.
>
>    24" spark length = 0.76*sqrt 1000 watts
>
> note I used 1000 watts instead of 800 watts to allow for the
> filament power for the two tubes.  In some of the calcs here
> I didn't bother accounting for filament power.
>
>    At 15 PPS:
>
>    24" spark length = 0.86*sqrt 800 watts
>
> I think at some particular slow pulse rate
> the spark length diminished some.  I'm not sure though.
> If the staccato pulse rate
> is very slow, the spark will not appear continuous but will
> appear pulsed when viewed by eye.  When speaking about
> the efficiency of a staccato tube coil, it's best to give the
> staccato pulse rate because the pulse rate has such a
> dramatic effect on the power draw.  When the coil runs
> at 30 PPS, the sparks look almost as full as at 60 PPS.
> At 20 PPS the sparks look good too.  Each pulse rate
> has it's own interesting appearance and sound.  When
> the rate gets slow enough, down to 15 PPS or so, only
> a single sword like spark will be seen.  This sword spark
> will waver back and forth slightly as the coil runs.  This
> type of spark can be seen at my website, as well as
> other types of sparks.
>
> Basically if you optimize the VTTC for staccato, then it will
> not be able to run continuously without staccato.  The tubes
> will overheat.  So there's a tradeoff.  Either use a high plate
> impedance and permit the coil to run at the full 60 PPS
> (no staccato), and limit the spark length (even with staccato
> turned on).   Or use a lower plate impedance and only
> run in the staccato mode at 30 PPS or less to prevent the
> tube from burning up.  But longer sparks will be obtained.
> The coil can be turned up to full power without staccato
> for short durations, but not continuously.  Keep an eye
> on the tube plate and watch for excessive redness.  Turn
> down the power very quickly as needed.
>
> John
>