Hallo to everybody, in this topic we can put our thoughts about the relationship between the partnered coils and the various joule-thief arrangements: are there some points in common? How much can we increase a power gain?
I've started my little research taking, as a base, a video from YouTube where a german experimenter shows us how to light up - to a very decent brightness - a 10W led with a source of 2.7V/70 mA.
My attention has been captured by the above very simple, but curious, joule thief which makes use of a very huge toroid (respect to the "normal" ones commonly used in these devices) so I tried to make my own replica but without success... I've smashed my head trying to understand why I was unable to replicate a so STUPID circuit... then I've realized: the DIMENSIONS counts! Did you see Godzilla (the movie)? Heheheheh
In a post of mine (somewhere in this forum) I stated that the wire mass, in some cases, could do the difference.
Well: my replica didn't work as expected because MY toroid was extremely smaller than the one required by the circuit (mine was 3cm OD, 2cm ID, 0.5cm Height, 1 mm dia enameled solid copper wire, where the one required is 8cm OD, 6cm ID, 1cm Height, 5mm dia enameled LITZ wire - 540 unique micro-wires stranded, insulated each other -).
Ok, someone could argue that the total induction, the total impedance and the total capacity of the two arrangements DO the difference but, if it is so, does the LITZ wire plays an important role in the game?
A far as I know, this kind of wire is used in those cases where the skin effect is relevant (high currents and/or high frequencies)... what about if we'll use it in the contexts where, at the moment, we're implementing the various bucking coil's configurations?
With this question in mind I've wrapped some LITZ wires I had around: the base wire is made of 90 micro-wires embodied inside an ultra-thin silk coating/layer; the overall diameter is 1 mm.
I have wrapped 6 of them to form a cylinder-shaped braid (7 mm dia, 540 micro-wires in total) with a complessive wire length of 10 meters (just to be sure to have enough cable to wind a big toroid in the two opposite directions).
I think that a similar coil will be also interesting for the MrPreva's experimentation... more observations will come.