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Re: Building A VTTC

Original poster: "Steve Ward" <steve.ward@xxxxxxxxx>

Since the pulse rate is always some even division of 60, its pretty
easy to listen to hear the 30, 20, 15, and 10pps.  Below that you may
need a counter.  Most people have scopes or maybe a meter that can
count, i dont think i would bother putting a counter circuit into the
staccato controller.


On 8/21/06, Tesla list <tesla@xxxxxxxxxx> wrote:
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


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

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?


 > -----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