Is joule thief circuit gets overunity?

[TinselKoala]

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

Yes, I think you are confused, but not about what you are thinking you are confused about. You are confused about your confusion, probably.

"At the same vertical settings and the same baseline" in my post you quoted was meant to refer to the immediately previous shot in post 525, where I explain that for these two screens I am using the exact center horizontal graticule marker for both displayed traces.  Sorry I wasn't too clear about that; taking shortcuts sometimes often seems to wind up taking longer in the long run. This is to bring them closer together so that it's easier to see the temporal relationships.
The lower trace is the input current, measured as usual at point A4 so it shows negative values, and it's displayed at 100 mV per division. ETA: and the baseline is at the center horizontal graticule line.

[TinselKoala]

If anyone's interested in the NTE3037 phototransistor measurement, I've made another short video where I drive a white LED with the function generator, using a triangle and a sine wave, at around 3kHz, and I show the response of the phototransistor to the changes in brightness of the LED. It seems quite satisfactory at this low frequency.

The video is uploading and should be available in a few minutes at:
http://youtu.be/me3kPvrOLi0

[ltseung888]

One thing you must realize is that those traces were done with the tiny hearing aid battery that is mostly depleted. Here are some traces from this board for comparison to Lawrence's traces, that I just made with an alkaline AA battery that reads 1.304 volts unloaded... that is, it too is fairly well depleted.

I don't usually use this much input power, but this is more comparable to Lawrence's input.

In the first shot, Output, the top trace is the Voltage Output at B1, the bottom trace is the Current Output at B3. The top trace is set to 2 volts per division, the bottom trace at 100 mV per division. (The top trace is using the center horizontal graticule line as the baseline, not the line indicated by the number "1" to the right. The lower trace is using the baseline indicated by the "2".)  I am showing only a single pulse to make the point that the waveshapes are the same, except that my "60 MHz" analog scope isn't displaying the spike amplitude.... but I assure you that it is there. Timebase is at 10 microsec/div and the delay function is used to bring a pulse onto the screen window.

The second shot is the Input, the top trace is the Input Battery Voltage at A1 and the lower trace is the Input Current at A4. The top trace is at 500 mV per division and is using the center horizontal graticule marker as its baseline, not the number to the right. The lower trace is at 100 mV per division, is using the numbered graticule line "2" as its baseline, and clearly and repeatably shows values both above and below the baseline. No "invert" is used and the probe is positioned just like Lawrence's is wrt current direction. Timebase is at 50 microsec/div.

So you can presumably see clearly that, if Lawrence's board is OU.... then mine must be too, since it gives the same instrumental readings when powered and probed in the same way that his is..... excepting the appearance of the high-frequency spikes.

And your detailed explanation seems to concur with what I said: the LED turns on at the bottom of the valleys, at the point where the slope reverses, and the power represented by the decreasing voltage slope to that point is the power that is pulsed into the LED.

@TK,

From my experience of looking at the many JTs scope shots, your JT is likely to be OU.  If you have a Digital Scope with saving  CSV data capability, you can easily confirm it with Excel.  Your finding that a weaker battery shows more "crossing" of the zero line for Input Current is also correct - same as my results.

I have scheduled to go to Shenzhou tomorrow to work with Mr. Zhou and take more photos - probably with pretty models too.  That will be fun.....

[picowatt]

Yes, I think you are confused, but not about what you are thinking you are confused about. You are confused about your confusion, probably.

"At the same vertical settings and the same baseline" in my post you quoted was meant to refer to the immediately previous shot in post 525, where I explain that for these two screens I am using the exact center horizontal graticule marker for both displayed traces.  Sorry I wasn't too clear about that; taking shortcuts sometimes often seems to wind up taking longer in the long run. This is to bring them closer together so that it's easier to see the temporal relationships.
The lower trace is the input current, measured as usual at point A4 so it shows negative values, and it's displayed at 100 mV per division. ETA: and the baseline is at the center horizontal graticule line.

TK,

Me?  Confused?  Yeah sure, that would be a first...

Did you mean to say at "A2" point s opposed to "A4"?  A2 is the input CSR/battery junction.  A3 and A4 should be the ground ref at the opposing end of the input CSR to which probe ground leds are attached.

So, if the center of the graticule is the zero ref, it is strange that you never get to zero current (or even go slightly above the zero ref) like Lawrence does.  Could your Q1 base be leakey?  Just a thought, as that could be a sneak path for current.  Otherwise I can't figure why you're showing current draw ALL the time.  Am I correct to assume that connecting the probe tip used at A2 to the ref ground at A3-A4 puts the trace at the zero ref line?


PW

[picowatt]

TK,

Forgive me, I see that I am indeed confusing the A1, etc points.  Back to Vin, Iin, Vout, Iout for me!

Can I use the "must be gettin' old" card?

In you reply #522, The input current trace looks as it should, going to zero and possibly just above zero.

What is different now?

PW