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Re: Thanks for all the Help! Trying to tune the primary coil ... and a new question (fwd)
Moderated and approved by: Gerry Reynolds <greynolds@xxxxxxxxxx>
---------- Forwarded message ----------
Date: Mon, 25 Dec 2006 16:04:10 +0800
From: westland <westland@xxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Thanks for all the Help! Trying to tune the primary coil ... and
a new question
Thanks all for the advice ... I've got this sorted now.... I had wired
up Terry's filter fairly late at night, and sort of inverted one section
of hookups ... anyway, once sorted it works as advertised ... I gapped
the safety gaps so they are just barely wider than the spacing that
allows them to fire when the NST has 220 VAC input ... this lets the
main sparkgap fire. For setup I'm using a single gap with two brass
balls ... I'll move onto an SRSG once I get this working.
On tuning, I found one of Finn Hammer's old posts that stated the signal
generator and the oscilloscope should be attached across the capacitor
leads, with the primary basically hooked across these cap leads as well
(i.e., the SG shorted). Works.
One curiosity ... The secondary reads resonance at 205KHz ... I set the
primary without the secondary in the center (with 10.1nF cap) for
resonance at 205KHz (tap at about 14 windings). Now when I put the
secondary into the center, I know I should be looking at two peaks
surrounding a dip at 205KHz ... instead, I seem to get this dip up
around 250KHz ... is this normal to have this offset from resonance
when everything is together?
Thanks again for all of the help
Chris Westland
Tesla list wrote:
> Moderated and approved by: Gerry Reynolds <greynolds@xxxxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Sun, 24 Dec 2006 13:20:15 -0800
> From: Jim Mora <jmora@xxxxxxxxxxx>
> To: 'Tesla list' <tesla@xxxxxxxxxx>
> Subject: RE: Please Help! Trying to tune the primary coil (fwd)
>
> Hi DC,
>
> I would be interested in you schematics. I noticed in Baraboo you were using
> a tiny spark gap while adjusting for maximum power out. I didn't get a
> chance to ask you how that worked.
>
> Also, I am planning a 15 degree primary again on my 12" coil. How do you
> adjust the secondary height or is that depicted a fixed end cap?
>
> I managed to adjust my res freq pretty easy on my 8" coil but I would think
> this should be done with all the components in place as it will be when lit
> up.
>
> Thanks,
> Jim Mora
>
> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Sunday, December 24, 2006 8:29 AM
> To: tesla@xxxxxxxxxx
> Subject: Re: Please Help! Trying to tune the primary coil (fwd)
>
> Moderated and approved by: Gerry Reynolds <greynolds@xxxxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Sun, 24 Dec 2006 09:13:34 -0700
> From: resonance <resonance@xxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Please Help! Trying to tune the primary coil (fwd)
>
>
>
>
> I've sent the schematic to him off-list. I also sent some schematics for
> dynamic Q measurement of sec coil, measuring coeff. of coupling with a tank
> heater, and a small Tesla coil tuning indicator (used with coil live
> sparking) that we use for dynamic coil tuning.
>
> If anyone wants these sketches contact me off-list and I will email them to
> you.
>
> Dr. Resonance
>
>
>
>
>> I've gotten to the stage where I need to tune my primary tap point, and
>> I've run into a problem in trying to figure out how to wire up the
>> primary coil to find the resonant frequency. I initially pulled the
>> secondary, put it on a plastic base, injected RF from my signal
>> generator, and read the response off of my oscilloscope with a small
>> antenna set as the input feed. This worked well, and gave me a resonant
>> frequency of 205KHz for a 4" x 22" coil with a 5x16 toroid topload.
>> Here are pictures of the setup (sorry for the fuzzy initial picture)
>>
>> Secondary tuning setup Antenna:
>> http://www.flickr.com/photos/51115445@N00/331719458/
>>
>> Secondary base (so it doesn't fall over when measuring):
>> http://www.flickr.com/photos/51115445@N00/331719464/
>>
>> Secondary tuning setup:
>> http://www.flickr.com/photos/51115445@N00/331719457/
>>
>> ********
>>
>> So far so good. So I hooked up the primary and the MMC (which I had
>> tapped for 10.2 nF... see pic). But I couldn't figure out how to wire
>> up the tank circuit so that I could get a reading off my oscilloscope of
>> the response to the injected RF signal (I tried several configurations,
>> plumbing the Internet for sources, but couldn't get anything to work ...
>> my voltage rises were all in the over 1 MHz area).
>>
>> I decided to compute from readings off my RLC meter, and found that I
>> needed to tap near the end of my 14th winding (with the 10.2 nF cap) to
>> get a resonance of 205K. But even with this setup, I couldn't get the
>> scope to give me any readings at all in the low kilohertz rang. Here
>> are more pictures of the setup. I also tried to test the complete coil,
>> but that didn't work either.
>>
>> Measuring impedance of MMC:
>> http://www.flickr.com/photos/51115445@N00/331719460/
>>
>> Trying to measure resonance of primary coil:
>> http://www.flickr.com/photos/51115445@N00/331719462/
>>
>> Measurements for complete Tesla coil:
>> http://www.flickr.com/photos/51115445@N00/331719463/
>>
>>
>>
>> Can anyone give me advice on where I am making my mistakes here. From the
>>
>
>
>> descriptions I've read on the Internet, tuning the primary should be
>> straightforward (but no one tells you how to wire up the test setup). You
>>
>
>
>> are looking for two peaks with a valley at the secondary resonance
>> (indicating the secondary is drawing power away from the primary circuit)
>>
>> Thanks in advance for the help
>>
>> Chris Westland
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>> ____________________________________________________
>>
>> J. Christopher Westland, PhD CPA
>> Professor, ISMT, University of Science & Technology, HK Clearwater
>> Bay,Kowloon, Hong Kong
>> Tel: 852 2358 7643
>> Fax: 852 2358 2421
>> Mob: 852 9528 1745
>> URL: ihome.ust.hk/~westland
>> Mobile e-mail: chris.westland@xxxxxxxxxxxx
>>
>>
>>
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--
____________________________________________________
J. Christopher Westland, PhD CPA
Professor, ISMT, University of Science & Technology, HK Clearwater Bay,Kowloon, Hong Kong
Tel: 852 2358 7643
Fax: 852 2358 2421
Mob: 852 9528 1745
URL: ihome.ust.hk/~westland
Mobile e-mail: chris.westland@xxxxxxxxxxxx