Is joule thief circuit gets overunity?

[profitis]

this is completely offtopic but do any of you guys have any tantalum capacitors lying around?perhaps stuck on a old junk circuitboard?

[ltseung888]

Waveforms from a secondary coil on Board 135.  A 1 meter copper coil was wound around the toroid on Board 135.  A load of 50 ohm + 1 ohm was used.  The Secondary Coil Voltage was taken across the 51 ohms and the Secondary Coil Current was taken across the 1 ohm resistor.

The Secondary Coil gave much more flexibility.  Replacing the 50 ohm resistor with a variable resistor affects the current both on the Secondary Coil and that in the JT circuit.  Since the load is purely resistive in this case, the resulting power from this Secondary Coil is all positive.  This power happened to be more than that from the primary Output of the JT.  The sum gave a COP of 1.04 but that was at the range of experimental error of the Atten and the resistors.

[Void]

It's hard to know just how much the supply's regulation and filtering is affecting your measurements, though. Certainly you aren't going to be able to "recharge" your power supply from the JT circuit, as some people think happens with batteries! At low voltages, most bench supplies aren't going to perform as stably or cleanly as they do at higher voltages. There are ways to get around this by using external voltage dividers and heavy filtering, probably, but not many experimenters are likely to go to that much trouble to assure clean and precise low-voltage power.

Some experimenters have even been known to cite the power supply's own display meters, usually digital, for their voltage and current measurements. I kid you not.

The thing is though that I use my scope to measure and monitor the input voltage, and when my power supply is set to 0.5VDC output, the voltage waveform is very stable. Very little fluctuation. For whatever reason, the super cap (when charged to close to the same voltage as the power supply ) was giving a measured increase in efficiency. I am going to run the test again, and I will post my scope screen shots in case anyone wants to compare the waveforms when using the power supply and when using the super cap as input power source. There is some difference in the waveforms.

[TinselKoala]

this is completely offtopic but do any of you guys have any tantalum capacitors lying around?perhaps stuck on a old junk circuitboard?

I do, old and new. Why?

[TinselKoala]

The thing is though that I use my scope to measure and monitor the input voltage, and when my power supply is set to 0.5VDC output, the voltage waveform is very stable. Very little fluctuation. For whatever reason, the super cap (when charged to close to the same voltage as the power supply ) was giving a measured increase in efficiency. I am going to run the test again, and I will post my scope screen shots in case anyone wants to compare the waveforms when using the power supply and when using the super cap as input power source. There is some difference in the waveforms.

Well, that's good, but of course you realize that your power supply already has a lot of filter capacitance in parallel with its output, probably, and chokes in series; it's just that the caps in the power supply have their charge constantly replenished from the voltage regulator.
Certainly there will be differences in things like impedance of the three power sources (bat, cap, psu) so why shouldn't waveforms and measured efficiencies differ a bit?