Joule Thief 101

[Pirate88179]

Smoky1:

Now I am going to play devil's advocate:

So let's assume for the sake of argument that you get better run times for the LED in this stable resonance/oscillation mode.  It's a definite possibility, you never know.

So let's go back to something I said:  The transistor briefly "oscillates down in resistance" and conducts and when that happens the LED goes off and the coil starts to energize.  Then the transistor briefly "oscillates up in resistance" and the coil dumps some energy into the LED to light it up.

So you energize the coil in "small sips" and then the coil dumps those small sips of energy into the LED through "resonance."

When you strip that down to the bare bones, it's just like a DC-to-DC converter that pulses a coil for a very short time at a fairly high frequency and then dumps that energy into an output capacitor.  I think a typical pulsing frequency is around 60 kHz and they only pulse the coil for a fraction of a time constant for the maximum efficiency (reducing i-squared-R losses.)

So just like you can buy a small very high efficiency DC-to-DC converter that switches at 60 kHz, you can buy a small very high efficiency DC-to-current converter that switches at a high frequency and the current output can be set to drive an LED.

So perhaps behind all the smoke and mirrors about a "resonant Joule Thief" the basic operating principle is essentially very similar to how a DC-to-DC converter operates.  The fundamental principle is better efficiency through very small sips of energy that are then sent to the LED.  This reduces resistive losses in the main L1 coil.

MileHigh

MH:

Now you are talking.  You see, back in the "old days" us JT experimenters were told that this circuit is nothing new and does nothing unknown...or words to that effect.  My response was always something like....OK, then if this is known, why do we not see this used commercially then?  Because, at that time, members were really lighting some leds up for a very long time on a single AA battery.

Well, it was not too long after that when we began to see led garden lights that were solar powered.  Remember when those first appeared?  Of course, we could not help but take a few apart to see what was happening there and, low and behold, there was a chip that when we looked at the specs, was basically a solid state JT circuit.  Then, some companies (China, of course) began to hide this chip under a blob of gray epoxy.

Now, I am not making any claims that our researching and playing with the JT circuit led to their commercial use but, the timing was interesting in that it removed my argument I used with you expert electronics guys.

So, I began to research some chip JT's and bought about 40 of them, along with some others and, they do work quite well.  I also have a few dc to dc converters that perform well as a JT circuit.

I was corresponding with MarkE about the direction my interests had taken and he said he was working on something that was very efficient using a new chip.  Well, about 3 weeks prior to his death, he pm'd me with the info on that chip and I am going to get a few to play with.  I still have his pm saved here.

I know that you have always liked the good old 555 timer but now, as far as I can tell, we have some new technology that is better and more efficient (for this application) and will do everything we were doing in a much smaller package without winding any wire, ha ha.

So, I think it is a good idea to research what is now available and we can test these new chips.  I do not know this for a fact but, I suspect that somewhere in that silicon there is something that adjusts the base voltage as the input voltage drops.....  The tech for those garden lights is now getting a bit older but really, I have to say that for what they do, they do it very, very well.  Also, I love how the prices have dropped since their introduction.  Now, you can get an led garden light, complete with solar cell and charging circuitry and JT chip...including battery, and led, and an attractive case for less than $3.00.  It was not that long ago we were paying more than that for a single led, ha ha.

So, we shall see what happens.

Bill

[tinman]

Self charging JT

https://www.youtube.com/watch?v=tx3bpSKRuF0


Brad

[sm0ky2]

Self charging JT

https://www.youtube.com/watch?v=tx3bpSKRuF0


Brad

hmm,.. I wonder what would happen if you had a couple thousand of these....

[sm0ky2]

@ Bill

the "timing" was also interesting with the LED lightbulbs, and several other places JT's are now found
it could make a fairly convincing argument that these did not exist before the JouleThief fad occurred.

[tinman]

@ Bill

the "timing" was also interesting with the LED lightbulbs, and several other places JT's are now found
it could make a fairly convincing argument that these did not exist before the JouleThief fad occurred.

Blocking oscillators have been around since the 70's.
The great John Bedini was not the first to build/design a transistor switched pulse motor either--he just tried to lay claim to that.


Brad