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Registered Member #205
Joined: Sat Feb 18 2006, 11:59AM
Location: Skørping, Denmark
Posts: 741
Steve McConner wrote ...
Finn, that is the essence of the difference between "Mode 1" and "Mode 2".
In Mode 1 the burst length is exactly one "beat" of the two resonant frequencies. I don't know what happens if you carry on driving after the notch, but I seem to remember Steve W. told me it was something bad.
Daniel and I took a video of that, and it showed that we could save a lot of power input to the coil, without loosing streamer length, by cutting the PW to exactly the first notch. Thumper has lower coupling, so we setteled for 200uS.
wrote ...
In Mode 2, the burst length is long compared to one beat. Because the coupling is tighter than Mode 1, and also because the burst is longer.
Yes, but the primary and secondary are also not tuned to the same frequency, right? AFAIU, the primary has to be tuned to the low pole to allow this mode to develop
wrote ...
So the primary waveform has several notches, that just look like a ripple. Because the modes are driven unequally, one of them dies out and the ripple disappears, at which point you are "QCW" and, streamer loading and inverter I2T permitting, can continue driving as long as you like.
Really only the first one is anything like a "notch". My PLL driver would unbalance the two modes enough from the start that I never even got a first notch, just a kind of dent in the envelope.
I remember seing something like that, during tuning of the 6 musical coils. Seems so long time ago. I setteled for tuning the primary to the low pole since that was the wisdom of the time.....
wrote ...
Mode 2 is theoretically less efficient, but in practice it seems to work fine. Steve's QCW is an extreme example of a Mode 2 DRSSTC, but some of his other coils are extreme examples of Mode 1. They are points on a continuum, I'm sure you can make one that is Mode 1 and a half.
Sure, when we slide the tapping point of Thumper past both modes we see this, even without being able to extract any hard evidence from it
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
There are some relations between type of driver, primary tuning and mode of operation.
With a feedback driver: you get Mode 1 if the two coils are tuned the same, accounting for streamer capacitance. If you detune the primary in either direction, one of the two resonances starts to dominate and the notch gets shallower, tending towards Mode 2.
With a PLL you can't get Mode 1 at all as it has to choose one or other of the resonant frequencies. (the feedback driver can produce a waveform that contains both frequencies, but the PLL always oscillates at one frequency.) Detuning the primary makes no difference to this behaviour, it will always want to be Mode 2. A PLL driver should not be used for a coil designed to run in Mode 1.
In my old simulation work I ironically called Mode 2 "Ward Mode". Mode 1 was Antonio Mode, as Antonio de Queiroz showed that a notch could be created by tuning the PLL midway between the two resonant frequencies. But I couldn't get that to work: it's a zero, there is nothing for the PLL to lock to.
It is possible that the differences between modes 1 and 2 might get less significant as the streamer loading gets heavier.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Well I finally got a chance to run the coil again, it's been raining the whole of last week.
I figured I would try some MIDI out on this coil just to see how it responded. Even though this coil needs long PW to make it's sparks MIDI seems to run on it very nicely.
I got some nice 10 foot sparks to ground and also the occasional 11 footer to the step still off to the right. The current limiter is still set to 800Apk with it only occasionally tripping during ground strikes.
The next time I run I plan to collect some data, my run last night was ended early due to the blistering cold wind.
Registered Member #639
Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512
Nice to see that two completely different modes of operation can still yield these results. Was your coil easy to tune? Noticed my big coil needed to have the primary seriously detuned to compensate for the streamer loading. Took a while to find the sweet spot.
Do wonder how you play the chords. 2 tones I do understand but complete chords is something I don't grasp yet.
edit: Read your site. Just doing 2 tones per coil. Can grasp that
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Dalus wrote ...
Nice to see that two completely different modes of operation can still yield these results. Was your coil easy to tune? Noticed my big coil needed to have the primary seriously detuned to compensate for the streamer loading. Took a while to find the sweet spot.
Do wonder how you play the chords. 2 tones I do understand but complete chords is something I don't grasp yet.
edit: Read your site. Just doing 2 tones per coil. Can grasp that
Surprisingly I only moved the tap point 3 times I guess I got lucky.
2 notes and complete chords are played using the same logic, OR logic. You also have to decrease the PW of every note depending on how many notes you add. The more notes the shorter the PW has to be. This is to maintain a some what constant duty cycles depending.
Registered Member #639
Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512
Same as the code that I've implemented then. Just limited to two notes per output at the moment. My coil is a pita when it comes to tuning. Each time I up the power it needs to be retuned for the streamer load.
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10KVA DRSSTC (Complete)
I guess I got lucky.