Joule Thief

[MarkE]

Yes Mark that coil won't work in a JT for some reason, the resistance is not high, it's fairly thick wire, might need to wind one, maybe a resistor will do. I don't have any Schottkys yet, some ordered but I might get more, this is fun and useful. I need to order the small gate chips so I'll get some of those Schottkys too.

Tinsel I think when I adjust the circuits so that the switch turns on just before the coil finishes discharging then the current is already flowing in the right direction and it gives that push along with it. Even the JT wave form shows that now. You can see that the slope on the decline of the discharge gets clipped by the switch turning back on.

Is that good or better when voltage is zero ?

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Oh I see, is that transistor bad maybe ? I thought it was happening because of the extra turns on the base trigger coil, the yellow turns are extra ones two blue coils the same on there with the yellow added to the end of one for the base trigger.

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Tinsel with the Logic circuit I can cramp up the wave form by adjusting the frequency/pulse width and clip the back of the discharge off square, which increases the amplitude of the output, and makes it "square" or rectangle.

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P.S.Here's a pic of a few of my small inductors, the little one beside the one with blue tape is about a half inch diameter and
has 1.2 mH inductance but only a few turns and hardly any resistance.
Only 7 turns or so and it is really light, like it's core is not made of normal "metallic like" material.

If you are ordering parts, you could try these Schottky diodes as well.  They have a bit higher Vfw than the LSM115s but much lower leakage current.

http://www.digikey.com/product-detail/en/RB161M-20TR/RB161M-20TR-ND/926464

ETA here is another diode that is about as good as you can get for low Vfw  in the mA to 100's of mA range and low leakage:  http://www.digikey.com/product-detail/en/DFLS120L-7/DFLS120LDICT-ND/673201

[MarkE]

Note that in "CMOS osc 3" you have a very clear ringing that has a frequency very near 400 kHz. This is the natural resonant frequency. At present this is a loss, as power  sloshes back and forth dissipating a little on each cycle and the amplitude of the ringing diminishes to zero before the next "push" happens.

Removing the output capacitor and output diode would force all the energy to go through the LEDs.  There is good data around that shows that the highest energy efficiency from boost converters is direct discharge of the inductor into the LEDs timed to completely discharge the inductor.  The problem is that for any given peak current handling capability in the power switch the maximum power that can be delivered is much smaller than with the flyback rectifier and capacitor.

[Farmhand]

Here's a setup to drain the life out of a depleted AAA and run some LED's while charging the tiny NiMH batteries and running the LED's with 10.7 or so volts across them, when the AAA is fully drained by the JT the CMOS circuit continues to drive the LED's efficiently.

With the Source battery at 1 volt the JT is drawing 40 mA or so from the battery at 1.2 volts it draws about 60 mA or so ect..

The CMOS LED driver circuit is more efficient as compared to the JT, But won't run below 2.5 volts around about. It does provide a more stable output voltage across the LED's though. Surprisingy so.

With 10.7 volts across the LED's the output is about 1 mA x the 10.7 volts - but the 2 x 3.7 volt 20 mAh NiMH batteries are charging at 4.05 volts and just holding now.  As the JT power reduces the little NiMH's will begin to help it out. 

With this setup I can see/measure how much power I get from a AAA source battery (the input power over time) and the amount of output power as well.
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I just received my 2 x 2.7 volt @ 50 Farad capacitors, they are fairly large,  .

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If I swap the 3.7 volt NiMH batteries for a 25 Farad capacitor charged to 5 volts then disconnect the JT supply battery so no battery, it should run for several hours.  We'll see later on. Longer if I use better parts and a better designed circuit.

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We could store energy in a high Farad capacitor from electro-smog or environmental then run the low voltage booster circuit from that intermittently to charge the Boosted capacitor or battery, then use the higher voltage as desired.

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[Farmhand]

Wow at 0.47 volts the JT is still running at a stable frequency of about 86 kHz and outputting 4.5 volts max at the collector.

But running the initial battery voltage down also runs down the secondary battery voltage so that it all stops all of a sudden that way.

If I disconnect the input AAA battery when the secondary batt or cap is charged to 4.2 volts it will run on for some time I think.

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[Farmhand]

Well I ordered some parts from digikey and the postage was more than the parts cost. I had to change to the Australian website then the postage was 34 dollars, and they asked a lot of questions as to why I wanted to import the parts. Weird.

Anyway I got 20 of those 74AUC gates and some of the Schottky's MarkE suggested, some MPSA18 transistors, some 2N7000 mosfets and some 1N5819 diodes.

If I order from them again I will make sure I have the cart full. 

Thanks for the tips on the parts.

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I'm wondering if one of the 74AUC logic gates can be used in the place of the pnp transistor in a two transistor single coil "feed back" type oscillator, then it could possibly be turned on and off by a micro to maintain the boosted output voltage level.

Or once the boosted voltage is achieved the micro could take over switching the LV transistor, or just perform "gating" to keep the output voltage stable and not allow it to go too high.

The circuits naturally "gate" in burst mode when the input voltage gets real low, so the same voltage sense could adjust output power to maintain an equilibrium, or perform controlled dumping of the boosted voltage into storage batteries.

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