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RE: [TCML] Tesla Coil tuner - scope traces questions
Yes - the noise along the waveform. What is generating them? Just
wondering...
Can't wait for the week-end - a bit of time at last to work on the coil!
Cheers
T
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of bartb
Sent: 17 April 2008 02:07
To: Tesla Coil Mailing List
Subject: Re: [TCML] Tesla Coil tuner - scope traces questions
Hi Thomas,
The 8 MHz spikes? Are you talking about the noise along the waveform?
The coupling at 1cm below is 0.113, so a large change for a small height
shift. Probably even with sec to 1cm below is the range you'll need. 5cm
below is too low as k is 0.053 then.
Take care,
Bart
Ryckmans, Thomas wrote:
> Thanks Bart,
>
> Very helpful, thank you. I was wondering what was the origin of the 8
> Mhz superimposed spikes I see on my scope trace?
>
> At the moment my secondary is 5 cm below the primary - I will calculate
> the corresponding k, and try to rig something to move it up or down to
> see the effect on performance. I still have not finished the Terry
> filter, but the static spark gap is now on PPE instead of wood
>
> Cheers
>
> Thomas
>
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of bartb
> Sent: 12 April 2008 02:51
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Tesla Coil tuner - scope traces questions
>
> Hi Thomas,
>
> I revamped my model for your coil with the new primary specs. This is
> how JAVATC interprets the coil:
> http://www.classictesla.com/temp/ThomasRyckmans.gif
>
> and here's a JAVATC output for my inputs and outputs for your coil (most
>
> everything is in centimeters):
> http://www.classictesla.com/temp/Thomas%20Ryckmans.txt
>
> JAVATC showed 828kHz and the tune point should be about 3.25 turns
> (pretty darn close to your 833kHz measurement). According to your
> primary tapping measurements, this area was giving the greatest voltage
> rise. I think your analysis for what you observed is fine. The primary
> should be off by about 270kHz from turn 2 to turn 3 and this will affect
>
> voltage rise by about 35% on the primary scope observations.
>
> I put your primary even with the bottom secondary turn. Coupling is
> 0.135 which is nice! You should be sparking away. BTW, in the .txt file,
>
> look near the bottom at the static gap. I calc'd the 4 electrodes in
> there (ignore the RSG stuff as it doesn't apply). But in the static gap
> section, pay attention to gap spacing between electrodes. This spacing
> is a ballpark for your transformer. Opening that gap up will increase
> breakdown voltage and although this is certainly easy to do, it's not
> wise as the voltage can kill the transformer, especially if it's an NST.
>
> Take care,
> Bart
>
>
> Ryckmans, Thomas wrote:
>
>>
>>
>> Hello,
>>
>>
>>
>> I've used a signal generator to try and tune my small coil. Because of
>> the small secondary (Diameter=70 mm, about 480 turns, 15 turns/cm, 32
>>
> cm
>
>> height; measured L is 3.5 mH; top load a bit more than 7 nF and coil
>> self capacitance 5 nF) resonance frequency is quite high - about 760
>>
> kHz
>
>> calc and 833 kHz measured using a source.
>>
>> I am using http://deepfriedneon.com <http://deepfriedneon.com> to
>> calculate values
>>
>> thanks for having a look!
>>
>> For all measurments, secondary and primary were physically separated
>>
>>
>> 1. Here is a picture of my scope's trace when off resonance (1)
>>
>>
>>
> http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#518789176
>
>> 5716440722
>>
>>
> <http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#51878917
>
>> 65716440722>
>>
>>
>>
>>
>>
>> then I tuned the signal generator until I got (2):
>>
>>
>>
> http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#518789179
>
>> 1486244514
>>
>>
> <http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#51878917
>
>> 91486244514>
>>
>>
>>
>>
>>
>> strange looking wave form. It collapsed very near that frequency but I
>> could not take a picture. Is this the resonance frequency? Removing
>>
> the
>
>> secondary and reading the scope I got 833 kHz.
>>
>>
>>
>> Then I kept my source at 833 kHz and plugged in the primary in
>>
> parallel
>
>> with the tank caps and shorted spark gap. My salt water caps is now
>>
> 11.6
>
>> nF and my primary is inside diameter 110 mm, tube 8mm diameter, side
>>
> to
>
>> side spacing 10 mm as per bartb recommendations - I did rebuilt the
>> whole primary].
>>
>>
>>
>> Calculated inductance is
>>
>> 1.3 microH for 2.5 turns,
>>
>> 1.9 microH for 3 turns
>>
>> 2.6 microH for 3.5 turns
>>
>> 3.4 microH for 4 turns
>>
>>
>>
>> And to reach "around" 833 kHz with my 11.6 nF cap I would need a bit
>> more than 3.5 turns.
>>
>>
>>
>> Now for measurments:
>>
>>
>>
>> When tapping at 2 turns I get trace (3) with amplitude about 2.5
>>
> squares
>
>> x 50 mV = 125 mV
>>
>>
>>
> http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#518789180
>
>> 8666113714
>>
>>
> <http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#51878918
>
>> 08666113714>
>>
>>
>>
>>
>>
>> at 3 turns (Picture 4) I get amplitude 4.4 squares at 50 mV = 220 mV
>>
>>
>>
> http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#518789181
>
>> 7256048322
>>
>>
> <http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#51878918
>
>> 17256048322>
>>
>>
>>
>>
>>
>> And at 4 turns I get picture (5) 3.6 squares at 50 mV = 180 mV
>>
>>
>>
> http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#518789175
>
>> 7126506114
>>
>>
> <http://picasaweb.google.co.uk/Thomas.Ryckmans/TeslaStuff/photo#51878917
>
>> 57126506114>
>>
>>
>>
>>
>>
>> So I think I should get correct tuning between three and four turns...
>>
>>
>>
>> Is this analysis correct?
>>
>>
>>
>> Are these traces the ones I should expect?
>>
>>
>>
>> I thought I would get a much more marked effect around resonance!
>>
>> Also - what is the origin of the small spikes in the three last
>>
> traces,
>
>> especially picture 5?
>>
>>
>>
>> Is this what is called ringing? I estimate the frequency of the small
>> spikes to be around 8 MHz or so...
>>
>> And why is the amplitude so low? My source delivers about 4 volts
>> without load
>>
>>
>>
>> Many thanks for your comments - as usual
>>
>>
>>
>> Thomas
>>
>>
>>
>>
>>
>> _______________________________________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxxxxxx
>> http://www.pupman.com/mailman/listinfo/tesla
>>
>>
>>
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