Coil Ringing - Good/Bad?

[PetersonElectric]

hello Bob,
I have found, while watching the oscilloscope, that the point of the circuit first starting to oscillate is the spot that charges the battery fastest, I presume because the frequency is much higher than with the rotor, but also the amplitude potential of the spikes are still very high. And at this point it is still drawing about half of what it would with the rotor. I'm not sure if this is the same sweet spot as yours, and the one you have been describing, but this is what i have noticed. I haven't experienced any overheating issues yet either, but that is probably because i have been using the same batteries.

Also i have notice that when charging and object, what ever it is, the tone increases as the object charges, so I predict that the rate of charging decreases as the battery (or whatever) gets charged more, like a logarithmic graph, probably until the circuit stops oscillating when the object is fully charged. and this maybe could be counteracted by changing the resistance periodically.
I was curious if my predictions are correct and if you have noticed anything similar to this.

[BobZilla]

Hi Peterson,
I would agree with your statement about the spikes at the first oscillation. I am at a disadvantage because I do not have an O-scope. I would say this; it is only guessing so don't take it as fact. The reason is that at that point you are getting a good crisp pulse across the coil, not over saturation. The way these systems work is too get the voltage across the coil but we don't want the current to move(well as little as possible), and then rapidly switch it off. The collapsing field pulls in the radiant so if we go too hard or too fast we do not get a good collapse before the next cycle and that makes the spike weaker and in extreme cases heat buildup. I have been playing with a large setup and I think I may be having this very issue, not the heat but I may be trying to drive it too hard with current and hurting the spike..

On the second point I have observed the tone increasing. I have experimented with putting a cap across the pot and a diode on the way to the base which is Patricks (Min2oly) mod by the way not mine. If done with the right values you get a very nice trigger pulse. While experimenting with that I used big caps & small caps. If you take an AM radio and dial it in to a dead spot you can listen to your circuit this way. At one point I put two 160uf 330v flash-caps in parallel across the trigger and with the radio I could really hear them wind up. The tone started very low and climbed higher, higher, higher, then the cap dumped and it started over again. I don't know if this is the same as you are referring too but it immediately came to mind when you mentioned it.

There are many others here on the forum with MUCH more experience than myself. Perhaps some of them will chime in. Keep tinkering and share your results with us in the meanwhile. It's nice to see someone like yourself coming to discuss these things. ---Bob

[PetersonElectric]

Thank you Bob, yes my next plan is to make a larger device, specifically designed for self oscillation and do more extensive testing with that, and post my findings with that