Re: [TCML] JAVATC & tuning

[futuret@xxxxxxx]

 Dennis,

As Bart mentioned, JavaTC doesn't take into account spark loading.
Capacitive spark loading can make the actual tune point somewhat different than
the JavaTC tune position.  As Bart mentioned, he's seen up to a 13% difference
in tune point due to spark loading.  I think it would be interesting if Bart added another
additional tune position output for his program which would suggest a tune point based on
spark loading, based on the expected spark length for a given input power and
break rate, etc.  This could get tricky though.  It would just give a rough tune point,
but less rough than not accounting for spark loading.

Anyhow based on all this, my guess is that you have fewer than 1650 turns, and that
you do indeed have heavy build insulation on your wire.  It's the spark loading issue
that's confounding everything.  If you do a scope resonance test using a signal
generator, it will give the secondary frequency without spark loading, and should
show a higher frequency (fewer secondary turns).  Another test you can do drape
a breakout rod over the toroid, extending 6" over the side of the toroid, and run
the coil at very low power (barely breaking out), and retune the primary for longest
sparks under that condition (with very short sparks due to low input power).  This
way spark loading won't be much of an issue, and you'll get a truer tune point
based on number of turns on the secondary, without being confounded as much by the
spark loading effect.  

Cheers,
John

 


 

 

-----Original Message-----
From: otmaskin5@xxxxxxx
To: tesla@xxxxxxxxxx
Sent: Sun, Apr 11, 2010 6:33 pm
Subject: Re: [TCML] JAVATC & tuning



Hi Bart, thanks for rechecking my JAVATC calc.  Yeah, I had discovered I had 
erroneously checked the AWG box being which was giving me the weird negative 
space between turns (that was embarassing).  

The reason I was came up with 1516 turns is that I input the heavy build 
insulation thickness into the turns calculator.  The spool I bought from 
McMaster Carr said the wire diameter was 0.018 close to 0.0178 (which is 0.0159 
bare wire + 0.0019 heavy build insulation) so I used the heavy build 0.0019 
insulation thickness in the calculator.  After getting your email, I redid the 
turns calculator using single build insulation thickness (0.0011) and came up 
with 1652 turns, almost exactly the turns number you came up with. 

The only thing I can conclude is that the spool was mis-labled as to the wire 
diameter.  It would be too much of a coincidence that, using 1650 turns, JAVATC 
came up up with almost exactly the number of primary turns (19.2) as I found 
through trial & error tuning (19.3).  So I gotta believe I really got single 
build insulation and 1650 turns on my secondary.  The only times JAVATC was ever 
way off for me was when I entered a bad input.  

I'll see if I can borrow a O-scope to verify frequency, but I think the mystery 
is solved.  Thanks again.  Dennis Hopkinton MA

otmaskin5@xxxxxxx wrote: 
> Thanks Bart. Attached are specs & JAVATC output. One odd thing I found that I 
didnt notice before is, under SECONDARY COIL OUTPUT DATA, the Space Between 
Turns (e/e) indicates -0.30455 inch. Not sure why it's showing a negative 
number. On the turns calculator I entered both "0", but also tried it by adding 
in the insulation thickness (x2). When I run the program, the -0.30455 doesn't 
change. Length of Wire output shows 2627.4 ft. That seems a bit off too since I 
had a 3000 foot spool & wound all but 30 ft or so. Maybe the program isn't 
running correctly on my computer? Thanks for taking a look. Dennis 
> 
> 
> 
> -----Original Message----- 
> From: bartb <bartb@xxxxxxxxxxxxxxxx> 
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx> 
> Sent: Tue, Apr 6, 2010 10:47 pm 
> Subject: Re: [TCML] JAVATC & tuning 
> 
> 
> Hi Dennis, > > Tuning will vary a little with surroundings (external 
capacitance) depending on the items nearby and even the coils sensitivity to 
extC. 2 turns is a bit much, so I understand your reason to question it. I've 
found (and many others) that a coil runs better when the primary is tuned for 
more L. Thus, it is actually "detuned" as far as coil to coil oscillation is 
based on their component values and derivations. I've run as far as 13% detuned 
on the primary in the coils I've built. In your case, your also running high on 
primary inductance as indicated by "more" turns. There are two main reasons why 
this occurs: 1) spark length and it's external capacitance affect on the coil. 
2) External objects affecting the coil itself. Beyond these main issues, there 
is also a 3rd. If the coil is relatively small in size, the primary L is often 
very small. Thus, a little extC can greatly affect tuning. This aspect is 
difficult to understand until you actually try it. > > In the end, what matters 
is your best spark length. Don't worry so much if a programs tuning is not 
perfect for your coil. Programs are using the best information they have, 
however, there's only so much data that a program can input that is practical 
for coilers. There is a point where more accuracy would require some odd 
measurements that most would not be up for or have the capabilities to do. > > I 
would like if you sent me your coil specs however. A Javatc output would be 
good. > > I haven't been checking my emails as often as I use to. I've been 
rather lazy with TCML this year. I do poke my head in now and then. I'll try to 
do better in the future. > > Very best regards, > Bart B. Anderson > > 


 
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