Is joule thief circuit gets overunity?

[TinselKoala]

Comments on your Slide12, the Board 80 input measurements.

In the first place your RMS voltage reading is irrelevant. Your scope trace in CH1 indicates fully 1.50 volts or more except in the "valleys" which are not "back emf", they are simply the dips in voltage caused by the LED turning on for a brief instant. Only the instantaneous voltage values are relevant to your power measurements, the RMS values only obfuscate the true issues.

In the second, most important place: Your WHITE LINE in your CH2 trace is a misrepresentation if it is supposed to be "zero" volts. Look at where the little bluegreen "2" symbol is to the left of the display area. THAT is where your "zero" value is, slightly above the major graticule line, not where you have drawn your white line which is almost a full minor division BELOW the graticule line. And the only part of your trace that is in any sense crossing this true zero line is .... NOISE, and perhaps a tiny ground bounce. And of course we recall that this probe is inverted, so negative values mean.... entirely conventional, battery discharging, power dissipating in the circuit, current flow.

[TinselKoala]

Some comments on your Slide13, the Board 80 output measurements.

Once again, you are citing RMS voltage values, which are entirely irrelevant here. Only the instantaneous voltage and current (voltage drop) values have any relevance to power and energy calculations done in this manner.

But more importantly..... you are STILL not putting your channel baselines directly and exactly on a horizontal graticule line. This is IMPORTANT for observers to be able to interpret easily your scope images. Those wiggly lines have meaning! Lots and lots of it. You are making it harder than necessary to interpret those meanings, and indeed actively obfuscating some details, by your sloppy positioning of your baselines. Positioning the baselines correctly allows one to see at a glance the voltage levels concerned.

Also, you are still putting your Trigger right on top of your baseline. Fortunately the Atten scope has a fairly intelligent trigger and isn't too upset by your attempts to fool it. Please place your trigger decently above your baseline level, so that you know that you are not going to be triggering on noise, and so that the T indicator doesn't obscure the 2 of the baseline indicator, displayed to the left of the trace area.

Your parameters panels do not provide the information necessary to determine energy performance at all, so please do not suggest that they "indicate possible OU".

I find it remarkable that this board is producing "exactly" 3 kHz signal.

[TinselKoala]

And finally, for this round.... your input and output measurements are not synchronous, being taken on two different scopes. Would you please show a set of traces obtained in the following manner: Use Scope 1 to monitor the Input Voltage and the Output Voltage. Use Scope 2 to monitor the Input Current and the Output Current. This will allow us to see the time and magnitude relationships between Input and Output directly, something that we have not yet seen from your arrangement.

When a nice 4-ch scope is used we'll have all of this data on one screen which will make matters much easier to interpret.

[ltseung888]

And finally, for this round.... your input and output measurements are not synchronous, being taken on two different scopes. Would you please show a set of traces obtained in the following manner: Use Scope 1 to monitor the Input Voltage and the Output Voltage. Use Scope 2 to monitor the Input Current and the Output Current. This will allow us to see the time and magnitude relationships between Input and Output directly, something that we have not yet seen from your arrangement.

When a nice 4-ch scope is used we'll have all of this data on one screen which will make matters much easier to interpret.

@poynt99:

We are now all earger to see your 4-CH scope results.  Sorry to put the pressure on you.

@TK:

The Vrms display is left from history.  Five Years ago, I did not use oscilloscopes and relied on voltmeters and ampmeters with AA batteries as source.  There was discussion that the correct way was to see the entire waveform and use the equation:
Intanstaneous Power = Instantaneous Voltage x Instantaneous Current.
If there were pulse elements, the closest value is the Vrms - not Vmax, Vavg etc.  At that time I called such displays "Tseung index" as a comparison for my many FLEETs.  They are still useful when I compare different JTs.

I enclose the scope analysis for Output and for Input as you suggested.  The numerical or absolute value for Average Output Power is greater than the Average Input Power.  If we agree that the COP is the ratio of Average Output Power over Average Input Power, we get COP > 1.

Let us let poynt99 comment on that - with the results from his 4-Ch scope.

[picowatt]

TK,

Referring to the schematic in your post 469 a few pages back, if you draw a short circuit between the A3-A4 point (scope grounds) and the A1 point, you will have maximum current flow thru the input side CSR.  Assuming for the moment that the battery (and the short circuit) has an infinitely low internal resistance, the measured voltage at A1 would be zero volts, and at A2, the voltage would be -1.5V (assuming a 1.5 volt battery).

Current flow would threfore be 1.5 amps and the actual battery voltage would be (A1-A2), which is 0-(-1.5), or 1.5volts.

In the recent captures, the negative going ripple on A1 is due to Vdrop across both Rint and the CSR when current is being drawn from the battery.  Any negative voltage observed at A2 represents current drawn from the battery.

Therefore, the negative dips/ripples on the A2 voltage are due to Q1 turning on and loading the battery with the toroid, which  produces current flow thru the CSR and causes A2 to be a negaive voltage (base curren is also drawn to a lesser degree).  During the Q1 on time, the voltage across the LED is effectively Vce(sat), so the LED is turned off because the voltage at B1 is below Vled(on) during this time. (this assumes the schematic as drawn in your 469 without a second battery in series with the LED).

When Q1 turns off, the voltage at B1 rises above Vbatt as the energy stored in the toroid discharges in series with Vbatt.  The voltage at B1 is clamped at the LED voltage as the LED turns on briefly (the B1 LED voltage must also be corrected by subtracting the output CSR Vdrop similar to the A1 Vbatt correction).

As the waveforms contain some fairly high frequency components/harmonics, all of the caveats regarding wiring inductance relating to accurate voltage/current measurements must also be considered.

That's my take on it...

PW