Is joule thief circuit gets overunity?

[ltseung888]

Third Check on Board 80 for the Hong Kong Government.
Average Input Power  = -0.047051
Average Output Power = 1.43838
COP =-30.57

It appears that the COP is higher with higher Input Voltage.  Will try to increase the Load and see the result.

[poynt99]

Lawrence.

Are you still using AC coupling on your oscilloscope measurements?

If so, why?

Have you been using AC coupling all along?

[TinselKoala]

@.99:
All the scopeshots on this page appear to have been taken using DC coupling. The coupling symbol is right next to the CH1 (or CH2) vertical gain setting. It's the standard dotted-over-solid international symbol for "DC". When the channel coupling is set to AC, this is replaced by a little "sine wave" symbol. Hopefully this DC coupling setting was also used when the spreadsheeted data were taken.

But don't you find it odd that Lawrence compares input data taken at one frequency, with output data taken at an entirely different frequency, at least according to the last set of scopeshots?

[ltseung888]

Lawrence.

Are you still using AC coupling on your oscilloscope measurements?

If so, why?

Have you been using AC coupling all along?

@poynt99

No,  All results shown in this thread used DC coupling as pointed out by TK.

AC Coupling was used to show the fluctuation in Input Voltage even though the probes were connected across the battery.  The ripple on the battery voltage correspond closely to the voltage variation across the 1 ohm csr.  Please use DC Coupling in your measurements.

[ltseung888]

@.99:
All the scopeshots on this page appear to have been taken using DC coupling. The coupling symbol is right next to the CH1 (or CH2) vertical gain setting. It's the standard dotted-over-solid international symbol for "DC". When the channel coupling is set to AC, this is replaced by a little "sine wave" symbol. Hopefully this DC coupling setting was also used when the spreadsheeted data were taken.

But don't you find it odd that Lawrence compares input data taken at one frequency, with output data taken at an entirely different frequency, at least according to the last set of scopeshots?

@TK,

Thank you for bringing up the frequency issue.  I just checked.  In the last case, the DC Power supply was set to 2V (close to the 2.3V 10F capacitor specification).  The frequency kept increasing even though the other readings remained more or less the same.  This particular happening did not occur at the lower Input Voltage setting.  The high limit for tests on other Boards were at 1.5V.

I shall redo the test at 1.5V and investigate this particular result later.  Thank you for pointing this out.

@poynt99,

Your 4 channel scope will be able to display Input Voltage, Input Current, Output Voltage, Output Current waveforms at the same time.  There will be no errors due to measurement at different frequencies.  Your data will add to our understanding of what is going on.  Thank you in advance.