Is joule thief circuit gets overunity?

[picowatt]

TK,

When you get the time, see if you can duplicate the reply 522 scope shots.

Particularly with regard to the Iin trace.

Could the Iin channel not be correctly set at your zero ref line "2" in that post?

PW

[TinselKoala]

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

Now you are really confusing me. I am using the letters and numbers as shown in this schematic attached below. I have always used these numbers, and I thought that everyone else was doing so as well. Is there a more recent schematic showing the test point locations? The only difference is that there is no capacitor on my board, nor on the ones Lawrence is testing now, right?

There is No probe tip at A2. A2 is NOT the junction of the input battery and the input CVR. CSR, whatever. A3 and A4 are NOT connected together, there is the input CVR between them. There is a probe tip, the input current probe, at A4 and its reference ground lead is at the common circuit ground at A2A3B2B4. As shown in the schematic below, and as noted in the legend of my photo of the PCB board above.

A2, A3, B2 and B4 are all connected together as shown in the diagram as the common "ground" and as I have noted in the legend to my photo of the PCB above. A1 is the battery positive terminal. A4 is the battery side of the input CVR, and this gets the current probe TIP, and so winds up being inverted.

Yes, grounding the probe tip to its reference lead produces the same baseline as switching the channel coupling switch to "ground". Yes, with weak input battery I get the input current trace "apparently" crossing the zero line and with stronger batteries it does not do so.

As Lawrence has confirmed, the stronger the battery used, the greater the "residual" or leakage current and the further negative the input current trace goes. What I find remarkable is that the wave shape itself is the same, even though it can move up or down wrt the reference depending on the battery's state of charge.

In the photos that show the PT output, there is NO connection between the PT circuit and the JT circuit, except thru the instrument ground leads, and there is no way that power can get from the PT supply to the JT, or vice versa.

Can't handle the letters and numbers, eh...?

[TinselKoala]

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

Ah, OK, I replied to your last post before I saw this one. So we are clear on the letter-number designations now? 

Lawrence says that he too has noticed that stronger input batteries lower the entire input current trace and that weaker input batteries are more likely to show the zero-crossing behaviour in the input current trace. The difference you ask about is that the 522 trace was made with a depleted button cell, either a LR44 or a 392, I've used both, and these cells cannot provide the current output that a AA can, even if the AA is relatively depleted. The later traces were made with a little stronger AA, and then the last ones by your request with a new AA, and it showed the most negative current trace (most residual or "leakage" current). Since Lawrence's systems behave the same way, this is more "evidence" that our circuits have similar performance when tested similarly.

EDIT: Sorry, I see now that my notes say I used a AA battery that was at 1.3 v unloaded for those traces, not a button cell. Apologies, things are moving fast and my lab is in chaos, as you can probably tell.

[TinselKoala]

TK,

When you get the time, see if you can duplicate the reply 522 scope shots.

Particularly with regard to the Iin trace.

Could the Iin channel not be correctly set at your zero ref line "2" in that post?

PW

Ah, I see now that I used a AA battery that was at about 1.3 volts unloaded for those traces. Sorry, I thought I had used a button cell.
I'm sure I can duplicate it, I've got plenty of dead and half-dead AA cells lying about. But the scopes are cold for the night, I may get to it tomorrow or later in the morning.
Yes, I checked the baseline position several times both by the coupling switch set to Ground and also by manually shorting the probe tip to its ground clip.  The zero-crossings are as real here as they are in Lawrence's boards.
Check back in the morning, I'll see about reproducing it again.

[ltseung888]

@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.....

I am puzzled that wih only an analog oscilloscope, how can one do the spreadsheet analysis?  Without the spreadsheet, how can one do the multipliction and averaging of thousands of sample points?