Is joule thief circuit gets overunity?

[picowatt]

PW.

Agreed.

.99,

If one looks back at many of Lawrence's posted waveforms, and corrects for 10 to 12mv of offset, only his more distant past examples that had sharper transitions indicated positive current excursions significantly above zero on the input side, which would be consistent with inductive effects.

His more recent slower waveforms indicate no or only a little positive excursion when offset is corrected and these small excursions easily fall within the realm of the DC accuracy and DC gain error specs of the scopes.

PW

[poynt99]

Lawrence,

Here are some results from my first crack at your board #33 measured with a brand new 500MHz Tektronix DPO4054 ($12k). The probes used are 4 brand new 500MHz Tektronix TPP0500's ($620ea).

Before I captured the screen shots, I let the scope warm up for 45 minutes, then ran a signal path calibration to minimize any offsets within the scope.

The test setup.

More...

[poynt99]

The Input scope shots:

tek000 through tek005 illustrate how the Input Current trace (blue) changes with a changing Input Voltage (yellow). The input voltage is measured and noted in the bottom left of the screen (look at the "MEAN" value). For example, in tek000 the input voltage is indicated as 516.8mV.

The blue Input Current trace did not cross the 0-reference line through all 6 Input Voltages ranging from 0.51V to 1.35V.

More...

[picowatt]

The Input scope shots:

tek000 through tek005 illustrate how the Input Current trace (blue) changes with a changing Input Voltage (yellow). The input voltage is measured and noted in the bottom left of the screen (look at the "MEAN" value). For example, in tek000 the input voltage is indicated as 516.8mV.

The blue Input Current trace did not cross the 0-reference line through all 6 Input Voltages ranging from 0.51V to 1.35V.

More...

,99,

Talk about a Maserati of oscilloscopes...  can we all say "test equipment envy"? 

Beautifully clean captures.

Do you recall if and where Lawrence may have posted his scope shots for the board your testing?  Possibly a date range if I have to look.

It would be interesting to see if his input measurement of that board crossed the zero line, and even moreso if by about 12mv.

PW

[poynt99]

The Output scope shots:

tek006 through tek008 illustrate how the Output Voltage and Current wave forms vary as the Input Voltage is varied from 0.53V to 1.35V.

Not taking into account the drops in the CSR resistors, a rough COP can be calculated by dividing the average Output Power by the average Input Power for a corresponding Input Voltage.

Input Voltage (0.515V, and 0.53V)
Pout = 3.68mW
Pin = 5.66mW
COP = 0.65

Input Voltage (1.35V)
Pout = 39.8mW
Pin = 48.4mW
COP = 0.82

Short video of the Input Voltage sweep to follow...