Joule Thief

[Mk1]

Mark,
I am winding a MK1 on a blue toroid. It is both thicker or taller in the cross section of the ferrite, and bigger in diameter than the one I used before.

I could probably fit more than 13 up and 12 down (per side) with the extra space.

I am wondering if you have any reason that you use the number of winds you do?

I am assuming it is the best fit, but I can change it easier now than later, so I am asking now.

thank you,

jeanna

The only reason for the number of turns is to get the most out a given space, i usually test with one wire of the size i will use then put has many turns possible going one way , that gives me a idea of how many turns can be fitted nicely , on one row , lets say i want to make a mk2 i would take that number and divide it by 2 , mk3 by 3 etc. that gives me the number of turns i can fit one way , usually on the way down to keep it nice you can't fit that many so usually the way up has more turns then the way down.

That said all toroid are different so that first coil will also give me test voltage , because i test the test coil , first to get a idea of the toroid flux , and know then if the toroid is good for a mk design coil , also this is the point where i test the number of jt coil needed for that toroid , just enough, if you put to many turns on the jt side it lowers the pickup coil voltage and coil ratio.

Those data are needed to get the best results , since all toroid are different .Also try lighting a led both ways on the one way coil , it wont , but one the coil goes both ways the led will also do.

Mark

[jeanna]

The only reason for the number of turns is to get the most out a given space,

OK good.

Because, you also want all the wires to be able to touch the toroid, don't you? I think I remember from way back that there should only be one row thickness.

thanks,

jeanna

[Mk1]

OK good.

Because, you also want all the wires to be able to touch the toroid, don't you? I think I remember from way back that there should only be one row thickness.

thanks,

jeanna

Yes , that is part of the plan , by knowing the exact number of turns for the space then all coil will be touching the toroid on the out side but there will be a second row on the inside since it smaller but on the out side there will be enough space for sitting them tight on the core not the other coils. also the data you have at that point will suggest adjustment like going to a smaller wire for more turns to get higher voltages. 

Mark

[xee2]

@ jeanna

OK all you scop-ies (scopie, noun = person who knows how to use a scope)

Where would YOU connect the ground probe if YOU were to test the secondary from a joule thief?

Please, if you don't mind, test a few usual places and see what seems to be right to you.

thank you,

jeanna

You can place the ground clip anywhere. But, unless you tell where it is no one will know what voltage you are measuring. Just saying I measured 10 volts is meaningless. You need to say what two places the voltage was measured between. To measure the voltage generated in a coil, you would connect the clip to one end of the coil and the probe to the other end. But if you do not say that is where you are measuring, then the reader could think you are measuring between some other two points.

[jeanna]

@xee2,

Thank you.

I will be clear that I measure between the 2 wires.

I assume the way to say this is NOT across since there is nothing it is across from. A cavern of space exists between the 2 wires, so I assume between describes it pretty well.

Really then, one becomes the ground or reference point for the other.

Thank you,

jeanna