Past days I have been playing with that modified "Joule Thief" circuit from my previous thread. I have "Bedinified" it and it does seem to use less current from the primary battery, although it's just driving LEDs.

I'm starting a new thread here because I'd like to know what others believe and know about the relationship between coil size VS ferrite (or air) core size VS number of windings VS frequency.

Using ferrite beads of different sizes I have wound couple of small feedback (flyback?) transformers for the above mentioned circuit. It's a simple bifilar setup with 20 or so winds of 30 AWG.

I've noticed that the smaller the bead the higher the frequency it seems, so the last one I made is a tiny cylinder bead which I can drive up to 120 KHz with the same component setup like the larger bead cores which go up to 70 and 40 KHz.
It also appears that the less current the circuit draws higher the frequency of the pulses (using a potentiometer instead of a resistor on the base to regulate the current draw)

I understand that we are dealing with time compression here so the pulses are shorter, but stronger (is the current higher then or the potential? what are we after?)

I'd like to know what kind of role does this time compression play, how is it used/applied and in general do we want to achieve higher frequency (shorter pulses) or not.

I am attaching a photo of my setup to make the post more interesting, but it is not indicative of the subject matter just to show the scale of things I'm experimenting with now.

Everyone's comments are appreciated.

Attached Images

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