Joule Thief

[resonanceman]

@resonanceman
http://www.google.ca/search?hl=en&q=selecting+a+transformer+core&btnG=Search&meta=
http://www.mag-inc.com/pdf/twc-s2.pdf  page 5

TheNOP

Thanks for the links

gary

[jeanna]

@jeanna

Thank You ! very much for all your detailed research !

you are welcome. I am grateful for your discovery.

...
Mark,
Would you please say this part again? I am not sure what you are saying here:

then the negative on the bridge and the out of the coil and your coil output .

Then the negative from the bridge goes where?

Maybe a little drawing? That is hard, I guess.

thank you,

jeanna

[TheNOP]

So, oscillation frequency then changes when the LED is put one way as opposed to the opposite way?

yes
the word "draw" is not an appropriate word to describe what is happening, the effect stay the same tho.
by adding the led one way, the impedance of the base coil is changing.

you can view impedance as resistance, but they are not the same thing, it is like apples and bananas.
a true resistance does not vary with frequencies, impedance does.



@jeanna
the values you get from different measurement methods are normal.

the values you see with your scope are peak values, you can also see the duty cycle and the frequency.

the values you see with your dmm across a bridge diode are average values.
still not true rms values mostly due to the duty cycle and frequency.

the values you see with your dmm across a bridge diode + capacitor, without a load, are cumulated energy.

the more spikes you have and/or the bigger the spikes, the more energy you get.

inductance is when the mag field one or more turn(s) of a wire affect an other wire.

self-inductance occure when the mag field one or more turn(s) of a wire affect other turn(s) of the same wire.
since the mag field can create a current flow in the wire next to it, if this happen in the same wire, an induced currents can flow in that wire ahead of the current creating the mag field.
that is why an inductance does not have resistance.


@resonanceman
one more thing about cores materials.
the most important factor is the frequency.
choose your core base on the frequency range you expect it to work at,
because you have to balance leakage inductance and Eddy currents lost.

but keep in mind that most values given for cores are mostly for ac currents.
the jt work on pulsed DC, not AC, so things like Hysteresis are not factors that matter.

[TheNOP]

Then the negative from the bridge goes where?

it is like connecting the 2 coils in series except that one coil is rectified first.

Ex:
connect one coil to a bridge rectifier
connect the + side to the other coil in series.
take measurement between the other side of the coil and the - side of the bridge.
or vice versa.

[Mk1]

@Jeanna

Thank , for the fast cap charging test on the cross windings , and this is a positive feedback system .

There is a mistake in my explanation the drawing is better. Tested on the mk2 each coil gave 76 volts 2 connected together 125 volts , and with the feed back 200 volts , it also raises the other coil by inductance i tested the setup on the mk8 and got the higher voltage in the other pickup coil also.

Pickup coil A and C are on the same side of the toroid , and B and D on the other.