Joule Thief

[Pirate88179]

Bill,
I do not think it is a resistance problem, 200 ohms should work. I am sure you have tried this, but, the first thing I try when a Joule thief doesn't work is to reverse the leads to one side of the transformer. If that does not work I would suspect something funny with the transformer. If you have a resistance meter able to read fractions of an ohm, you can check to make sure the collector coil has more resistance (more turns) than the base coil.


PS - Your transformers may have a different pin out than the Kodak's that  were used years ago. The Fuji transformers had many different pin outs.

Xee2:

Really?  That is interesting.  I just figured I didn't have the right resistance.  I hunted all over to find a source for these inverter transformers and finally found one.  They do not offer a schematic of the pin outs however.  OK, thanks, I will check the resistance of the coils.  This is really great information and I do appreciate it.  I just "assumed" that the inputs were the 2 pins and the outputs were the 3 pins.  They do not fit on a breadboard and, as I am sure you know, this is not easy to test unless you go ahead and solder the circuit.  I have many meters here and my best is an Omega so, hopefully, it will show me the resistance difference of the windings.

Thank you again.  I owe you.

Bill

[xee2]

They do not fit on a breadboard and, as I am sure you know, this is not easy to test unless you go ahead and solder the circuit.  I

Bill,
You may be able to test them without soldering leads on the pins. If you have two cables with alligator clips, try putting a stiff wire in the clip at one end of each cable and hook the other end of each cable to the meter. You may be able to get a good enough connection to make a measurement just by pressing the wires against the pins. No promises, but it is easy to try. Good luck.


PS - I suggest holding the transformer in a vise while you try this.

[SkyWatcher123]

Hi folks, have been pondering the gutted cree light have been using here, the one with the flyback or the yoke ferrite core and the non-polarized capacitor in series with the secondary coil and gutted led bulb.
As was mentioned previously, it just about cut in half the input amperage and doubled or so the light output, what is going on here.
So, checked the capacitor while oscillating and it sits at around 185 volts.
Then, disconnected the primary coil wire of the bifilar joule thief to just manually pulse and see what is going on.
Initially, when touching coil wire to 4 volt lithium cell, it lights up led bulb dimly, then when disconnected, it lights up much brighter.
Then if this pulsing is done a few more times, the capacitor must be filling up somewhat, then the initial coil wire contact with battery reaches an equilibrium and the first pulse starts to become equal in brightness to the collapsing pulse.
Also, sometimes, the collapsing pulse seems to be ringing down with the capacitor and it fades out slower, but it seems you have to get the pulses correct for that to happen.
Would really like to know what is going on here.
How can the led bulb be lighting both ways, when they are diodes and should not be conducting both ways, with initial coil pulse and collapse.
Also still trying to figure out why circuit uses half as much input compared to no capacitor and its doubling of brightness.
One idea, is that since the secondary capacitor is sitting at 185 volts, less average current is being reflected back to the primary coil of joule thief oscillator, though have no idea as of yet, to why the bulb is lighting both ways.
Any thoughts greatly appreciated.
peace love light
tyson
edit2: Ok, now think i have it.
Had to reorient the led bulb diode to comprehend it.
The initial pulse inducted into the secondary allows this pulse to cause the led diodes to conduct, until the capacitor charges, once that occurs, no more current can flow.
Then upon collapse of the secondary coil, since the collapsing pulse voltage from the coil is greater than the capacitor at any given moment, it does not matter that the polarity does not match the diode cathode or anode, as long as there is a potential difference, it will conduct.
So that is why it conducts both ways and charges the capacitor to 185 volts also, i thnk.
Though do wonder what the polarities are on the capacitor just before the coil field collapses into the capacitor through the diode, seems they would be opposite, creating a series connection, instead of parallel, though maybe someone has an idea on that.
Reoriented led diode in picture, because that is probably how it is wired now.

[Magluvin]

Hey Bill

Can you use a JT to charge say a 1uf or 10 uf cap to 100v pretty quickly?

Thanks

Mags

[TinselKoala]

I hope you don't mind me jumping in here.

http://www.youtube.com/watch?v=CAkgwBS8q4A