Is joule thief circuit gets overunity?

[TinselKoala]

TK,

I still think Board 80's waveforms look a bit different than yours.  Not just that the spikes are missing, but the general slopes on the tops of bothe the V and I waveforms appear to have a different rate.

As with regards to your last sentence above, I agree that the LED turns on at the bottom of the input voltage valleys, at the point where the slope reverses, BUT, I would state: the power represented by the decreasing voltage up to that point is the power being drawn from the battery and stored in the toroid (and as well disipated in Q1, the input CSR and the battery's Rint).

The LED turns on when no current is being pulled from the battery (Q1 is off). 

Actually the light curve shows that there is still some current drawn during the time the LED is on. The current doesn't return to (near) zero until the LED turns off. Please see the trace below, which is the phototransistor output and the input battery current.

As well, if there is any battery recharging from the collapse of the toroid, it is occurring during the rising portion of the Vin waveform from just past the most negative peak when the LED is on.  During that period (whilst the waveform is rising) the LED is on and current must flow thru the LED, output CSR, Input CSR, input battery, and the toroid to complete he circuit.  The collasing toroid acts as an additional battery in series with, and with a voltage higher than, the input battery.  The polarity is such that the current thru the LED and toroid tends to raise the terminal voltage of the input battery slightly during the LED on time.  So, if anything, the battery is actually recovering a bit of its charge when the LED is on.

The internal R of the input battery will affect the amount of ripple seen on Vin, and the amount of battery depletion determines the battery internal R.

What happens to your circuit with a fresh alkaline?

PW

I don't know, I'll have to try to find one.
In the traces below, the top trace is the output from the phototransistor looking at the LED's light. The bottom trace is the Input Current. Both traces are using the exact center graticule marker as the zero baseline.
The crossing of the zero baseline by the input current might be a DC offset error in the scope itself, especially since this signal is displayed at such a high amplification. In the shot below my input current does not cross the zero baseline, whereas using the weaker button cell and a different vertical attenuation, it did.

[TinselKoala]

Using an absolutely fresh Duracell AA that measured 1.617 V unloaded, I got the PT light detector output and current input traces below, at the same vertical settings and same center baseline. I also tried a much weaker battery. (The horiz setting is different, the fresh battery allowed quite a bit higher frequency for a while.)

The residual current is greater for the fresher battery. As the battery voltage decreases, the current trace gets closer and closer to the zero current baseline. For my system, I need to use a pretty weak battery to get the input current to appear to cross the zero baseline.

[TinselKoala]

Yes, I suppose the current in Lawrence's shots is decaying faster than in mine. And the significance of this is.... ? I think in his recent shots he's using some kind of rechargeable battery, isn't he?
Now I can't even remember what battery I used for this shot, but the two comparisons of Lawrence are the board 80 and another one from earlier in the thread.

[picowatt]

Using an absolutely fresh Duracell AA that measured 1.617 V unloaded, I got the PT light detector output and current input traces below, at the same vertical settings and same center baseline. I also tried a much weaker battery. (The horiz setting is different, the fresh battery allowed quite a bit higher frequency for a while.)

The residual current is greater for the fresher battery. As the battery voltage decreases, the current trace gets closer and closer to the zero current baseline. For my system, I need to use a pretty weak battery to get the input current to appear to cross the zero baseline.

TK,

What are these traces again?  Is the lower trace really the input current?  If so, where is the zero ref?  If it is at the masking tape with "2", then I am confused.

Could the lower trace actually be input V?

PW

[poynt99]

@PW, .99:
In Lawrence's recent scopeshots of Board 80, the one that I have edited to show the _true_ baseline for the CH2 current measurement.... note that the scope is reporting + 40.00 mV RMS for that signal...... which barely ever actually goes positive, never even reaching 40 mV positive that I can see, and extending deeply negative during its spikes.  RMS, of course, is mathematically always a positive value..... so how are we to interpret a _positive_ RMS value for a signal that is actually almost always, if not strictly always, negative? The RMS value gives the wrong direction for the current being measured in this channel, doesn't it?
Lawrence has explained that the RMS boxes are a "legacy" from his early work. I hope it's clear now that these values are not relevant and may even be confusing the issue, due to things like the positive RMS value for a clearly negative-average signal. They should not be displayed at all. If the scope has a simple "average" parameter available, that might provide some rough and useful information. An artificially positive RMS value does not.

Tk, dare I say you answered your own question. The scope is reporting a positive rms value because rms inherently is always a positive number.