Originally posted by NickZ
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The shorter ferrite rods will work fine, just place some turns on it an measure it to be 100uH.. If no meter, I suggest place 39 turns on each, that will be a good ballpark.
If you can't get the circuit to work at all, try switching ONE of the inductors its wires, or maybe turn the LED. (best to try with an 1.5v battery, to see if the circuit works fine on it).
The inductors as in the picture are my old ones, do NOT do it this way... Instead, wrap a piece of paper around the ferrite, and put a small piece of cello tape (E.G, the paper can now slide over the core).. then turn your windings on that paper and when finished, slide the paper -with the coil on it now- to the middle of the ferrite rod.. make both the same way.
Then when place your cell on it, see if you get can it to light continuous by replacing the 1nF capacitor, and by sliding the coils a bit, you can 'optimize' energy usage a bit... you can either give the transistors base a bit more juice -at cost at led power-, or decrease it a bit and give more to the led.... Sliding *both* coils to the same position (little bit off the ferrite) will lower induction and increase Frequency... So play around with the capacitor and coil positions, you will get a 'feeling' of how to tune it more optimally.
As per PM, you can leave out the current limiter pot, and the 2 big capacitors with the sense resistor, I use them to get exact measurements.
P.S the BLACK cap 'attached' to the potmeter in above photo is dummy... haha, the potmeter is a 'Philippines' quality product, thus its zero ohm is not zero but 8 ohm! , so i grabbed first object I saw to short the pot when i don't need its function, and that object happens to be that capacitor.
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Ron.
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