Joule Thief 101

[Magluvin]

Been studying

http://www.cliftonlaboratories.com/self-resonant_frequency_of_inductors.htm

http://www.g3ynh.info/zdocs/magnetics/appendix/self-res.html

Mags

[MileHigh]

For some(or one),this seems to be a little above there pay grade.


Brad

That's a double-shot of Planet Bizarro considering that the inductor current flows into the collector and it's the collector current that is relevant.

[SeaMonkey]

Very nice work on the Technical Literature Mags!

A serious experimenter would study it well and
even copy it to their hard drive for convenient
future reference.

Most browsers will save pages either as HTML or
Print the page as a PDF.

[MileHigh]

Yes,CH1 was inverted.
We can see we have 800mV at the base. What i wanted to show was the switch on curve,but the resolution on the scope was set to high,and the top of the wave form(the switch off spike) would have been out of the screen if i had decreased the VPD limit-and i did not want it flowing into the LED trace. So i just left it at that.

Brad

Yeah, sure it was inverted.... or was it inverted?  If it wasn't inverted, how do you get somewhere between a 10-volt and and 16-volt spike across a transistor base-emitter junction?  If it is inverted like you claim then how do you maintain somewhere between 10 volts and 16 volts across a transistor base-emitter junction?  You comment on the high-voltage spike in your clip and just walk past that totally wonky measurement like a zombie.  Why would you even put your probe across the base-emitter junction when there is so much more information to be learned if you put your probe on the output of the feedback coil?  You have a pretty big toroid so why is your setup running somewhere between 20 kHz and 30 kHz when Magluvin's ran at 4.2 kHz?

Look at the crappy zoomed-out waveform capture from your clip that isn't even capable of showing the waveforms properly because they are grotesquely undersampled and compare that to the nice clean scope capture that Magluvin did of a Joule Thief operating in normal switching mode with a nice zoom-in on the actual switching cycle so we can see what is going on.  We are back in "communication-skills-issue-elephant-in-the-room" mode for you.

I can't be 100% certain from your foggy clip, but all of the indicators are pointing to the conclusion that your Joule Thief setup is running in wonky spastic high-frequency mode and the base-emitter scope channel is not inverted and there really is a super-high voltage spike across the base-emitter junction of the transistor.  That's what you get when your Joule Thief is running in some unknown spastic high-frequency mode.  In other words, your "demonstration" is a total fail and a miserable embarrassment considering the fact that you have been doing this stuff for six years.

The clip is a complete disaster and proves nothing.

MileHigh

[Magluvin]

Yeah, sure it was inverted.... or was it inverted?  If it wasn't inverted, how do you get somewhere between a 10-volt and and 16-volt spike across a transistor base-emitter junction?  If it is inverted like you claim then how do you maintain somewhere between 10 volts and 16 volts across a transistor base-emitter junction?  You comment on the high-voltage spike in your clip and just walk past that totally wonky measurement like a zombie.  Why would you even put your probe across the base-emitter junction when there is so much more information to be learned if you put your probe on the output of the feedback coil?  You have a pretty big toroid so why is your setup running somewhere between 20 kHz and 30 kHz when Magluvin's ran at 4.2 kHz?

Look at the crappy zoomed-out waveform capture from your clip that isn't even capable of showing the waveforms because they are grotesquely undersampled and compare that to the nice clean scope capture that Magluvin did of a Joule Thief operating in normal switching mode with a nice zoom-in on the actual switching cycle so we can see what is going on.  We are back in "communication-skills-issue-elephant-in-the-room" mode for you.

I can't be 100% certain from your foggy clip, but all of the indicators are pointing to the conclusion that your Joule Thief setup is running in wonky spastic high-frequency mode and the base-emitter scope channel is not inverted and there really is a super-high voltage spike across the base-emitter junction of the transistor.  That's what you get when your Joule Thief is running in some unknown spastic high-frequency mode.  In other words, your "demonstration" is a total fail and a miserable embarrassment.

The clip is a complete disaster and proves nothing.

MileHigh

Ive had 18v peaks across my white led. So his max is not unrealistic. Laser mode. Led overdrive.

Mags