Joule Thief

[Mk1]

@all

On a bifilar jt , the pickup coil needs to be starting and ending at the same location , if the pickup coil goes over the end or start of the pulsing coils it usually doesn't work.

Mark

Edit slayer007 had the same problem at first.

[xee2]

@ jeanna

He is making high frequency sparks pass through a wire. The wire or the entire space between 2 wires or the wires themselves etc. become illuminated.

I think this is referring to things like neon tubes. If you look at the electrodes in a neon bulb they seem to be glowing. But actually it is the ionizing gas at the surface that is glowing. In a long neon tube, the gas between the electrodes glows. But this takes a very high voltage.

[TheNOP]

@xee2, Is the sparking the same thing as the capacitive coupling you EE educated guys talk about?

no
the sparkes occure when the voltage(potential) between 2 wires is greater then what the dielectric can support.
the potential difference ionise the dielectric to the point it start acting like a conductor.

[xee2]

It is quite common to put the primary over the secondary. It is the way most auto ignition coils are made. So I do not understand why it would be a problem in a JT. The following drawing is from http://www.familycar.com/CLASSROOM/ignition.htm

[jeanna]

This site is doing a funny thing today. I just returned after having given up and I find that my post was indeed accepted. crazy.

So, after a long delay,

@MK1, Good clarification. thanks.

@xee2, It may have turned into neon tubes but during that lecture to the London EE's I quoted the words he used to introduce a demonstration of several examples of wires vibrating at high frequency which passed very small sparks evenly across the space between them through the open air. He even used a single strand in a way to glow with sparks.

The point of my question was that perhaps this tiny sparking is occurring across the air around the toroid whose overlaying primary is creating the very high frequency. Perhaps when the secondary is so close to the toroid this is made a worse problem.

Hazens has not complained about this and his magwire has a thicker coating than the RS magwire, I believe.

Anyway, Dog812, I am only saying it may NOT be worse. It may actually be more successful, but in being more successful, it may have a sparking problem coming along unexpectedly.

And
Thank you theNOP and xee2. I now know this is not what capacitive coupling means.

thanks all,

jeanna