In one of the circuits under the name of Dave Lawton, the circuit doesn't seem to use a pickup coil in the transformer, instead a pair of capacitor is used to detect the signal directly from the cell itself.



Could someone explain few points about this.
1. The circuit indicates that the capacitor must match the cell. what does it mean.
2. By detecting the signal directly from the cell, what kind of benefit one could get, for example detecting the real resonance frequency hitting the cell.

Has anyone tried this setup and found to be simple/useful.

I don't think there is any benefit to monitoring for resonant feedback directly from the cell.  The transformer core is the source of changes in frequency and phase. 

From international patent WO 92/07861 page 9:

Quote

The magnetic field of the pulsing core is in synchronisation with the pulse input to the primary coil.  The potential from the secondary coil is introduced to the resonant charging choke(s) series circuit elements which are subjected to the same synchronous applied electromagnetic field, simultaneously with the primary pulse.

When resonance occurs, control of the gas output is achieved by varying voltage amplitude or varying the time of duty gate cycle.  The transformer core is a pulse frequency doubler. ...

From page 10:

Quote

Figure 7, a phase lock loop, allows pulse frequency to be maintained at a predetermined resonant condition sensed by the circuit.  Together, the circuits of Figures 7 and 8 determine an output signal to the pulsing core until the peak voltage signal (Not level) sensed at the resonance is achieved.

We have 4 rules in these few paragraphs. 

• The core magnetic field is in synchronization with the primary coil input pulse
• The choke coils and secondary coils are also in synchronization with the core
• The transformer core is a pulse frequency doubler
• The phase lock loop maintains pulse frequency at a resonant condition sensed by the circuit.

I have been able to see this frequency doubling on my scope with the pulse indicator circuit.  This is with a VIC transformer with a "shot in the dark" number of winding turns on a chipped up fly-back transformer core, and a small neon bulb in place of a cell.  The input frequency was exactly half of the pulse indicator frequency.  With messing around with the load, I could change what frequency this doubling occurred. 

This would appear that the pick up coil working with the core has a method of knowing when the cell it's self is in a resonant condition, rather than the coils being in resonance with each other.  Having the coils in resonance with each other is a function of design, and I don't believe a scanning circuit is needed to find that resonant condition. 

So at the point of achieving a frequency doubling on the core, the PLL is going to sense this condition.  It's job is to keep the input to the primary in synchronization with the core.  The phase lock loop is also some times called a frequency synthesizer, it has the capability of matching this double frequency it senses in the core, and sending a clean tailored copy of that frequency back into the primary coil. 

The pickup coil,  pulse indicator circuit, and phase lock loop are like steroids for a finely tuned set of VIC coils. :cool:

Nate