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Author Topic: Is joule thief circuit gets overunity?  (Read 537626 times)

Offline picowatt

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Re: Is joule thief circuit gets overunity?
« Reply #540 on: April 10, 2013, 10:15:56 PM »
TK, Lawrence, et.al,

Because I now realize I was using odd assignments for channel 1 (A1=CH1 probe, A3=CH1 gnd) and even assignments for channel 2 (A2= CH2 probe, A4=CH2 gnd), I am reposting the following with corrections.  It proably made very little sense as it was!

The main point here was to assist in visualizing the correct polarity of the voltage measured at the input CSR when the battery is discharging.  Past posts I read here pointed to a bit of confusion regarding this.

TK,

Referring to the schematic in your post 469 a few pages back, if you draw a short circuit between the A2-A3 point (scope grounds) and the A1 point (batt+), 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 (batt+) would be zero volts, and at A4 (batt- and CSR), 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-A4), 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 A4 represents current drawn from the battery.

Therefore, the negative going dips/ripples on the A1 voltage are due to Q1 turning on and loading the battery with the toroid, which  produces current flow thru the CSR and causes A4 to be a negaive voltage (base current 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 post 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...



Hopefully the above post will now make sense.

PW

Offline picowatt

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Re: Is joule thief circuit gets overunity?
« Reply #541 on: April 10, 2013, 10:21:39 PM »
TK,

I looked for, but could not find, the core specs and winding info for the toroid.

What did you use?

PW

Offline TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #542 on: April 11, 2013, 01:49:18 AM »

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?

Well, in the first place you don't really need thousands of sample points, if the sample points are selected intelligently instead of by rote, and in the second place..... how do you think people did these things before DSOs and easy-to-use spreadsheets were developed?  How, for example, was the first digital oscilloscope designed and tested?

One way that has been used in the past with great accuracy is to make an image of the scope trace on paper, then you cut out the waveforms carefully with scissors and you weigh the pieces of paper on an analytical balance.

Another way is to use, instead of an oscilloscope, an integrating power meter like a Clarke-Hess 2330.

Using a completely manual method on my scope displays of some traces from a different, but quite comparable, electrical OU claim, I was able to come to within a few percent of the "theoretical" values obtained from displaying the same traces on a 4CH DSO that did the necessary computations _of many thousands_ of sample points in real-time. Of course the manual process is painstaking and takes a good amount of time, like about 2 hours of sustained concentration to process a single screenshot.

The image below will give you some idea of one stage of the process as I implemented it. Please don't laugh, this really does work "close enough for government purposes" , and the issue of spikes and sampling errors is addressed by doing the process at the correct time scale resolution.

There are other ways, too, working from screen imagery of scopetraces. For example many graphics programs allow you to select or define an area, and then they will return the pixel count of that area, a very effective way of performing a graphical "integration".

Offline TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #543 on: April 11, 2013, 02:08:29 AM »
TK,

I looked for, but could not find, the core specs and winding info for the toroid.

What did you use?

PW
It's a green-painted toroid from a defunct PC PSU. It has a 10 turn primary of 1.08 mm enameled wire that was already on it, and about 55 turns of 0.70 mm enameled wire secondary that I wound onto it. The bare toroid is 20 mm in diameter.

And I also should point out that the PCB JT has a metal-can 2n2222 transistor in it, not a TO-92 2n2222a or even a metal can 2n2222a. However I am happy (more or less) to pull the one and put the other in, I have all three types in stock. But there are other transistors that will work even "better" if we want to get down to comparing equipment... so to speak. 2n2369a works well, MPSA18 is great.

Offline TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #544 on: April 11, 2013, 03:44:19 AM »
OK, ok, so I put a genuine TO-18 Motorola 2n2222a in there, along with trying a few other flavors. (The old one was a Motorola 2n2222). The plastic MPS2222a really surprised me. It didn't give a big brilliant light, but at less than 2ma PEAK current draw from the battery it will run for a long long time. The 2n2222a seems the best of the 2222 variants that I've tried but it's hard to see any difference with the 2n2222 by the same manufacturer at these frequencies.

I found a data sheet that shows the differences in ratings between the 2n2222 and the "a" variant.


Offline picowatt

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Re: Is joule thief circuit gets overunity?
« Reply #545 on: April 11, 2013, 04:39:07 AM »
TK,

Before you make too many changes, consider trying to duplicate the waveforms of your reply #522.

PW

Offline TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #546 on: April 11, 2013, 05:09:21 PM »
TK,

Before you make too many changes, consider trying to duplicate the waveforms of your reply #522.

PW

Yes, I have tried, both with the original transistor and the new one, using the same battery too, and I can't seem to do it. The traces always stay below the zero line. I am starting to wonder if I inadvertently set that channel to AC-coupled for that trace. It is barely possible that I flipped the channel coupling switch the wrong way after checking the baseline at "ground" coupling. I am having a hard time believing I would do that, though, since I did check the trace several times.

Awww... does that mean my little PCB JT isn't OU after all? I'm crushed.

Offline picowatt

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Re: Is joule thief circuit gets overunity?
« Reply #547 on: April 11, 2013, 05:24:49 PM »
Yes, I have tried, both with the original transistor and the new one, using the same battery too, and I can't seem to do it. The traces always stay below the zero line. I am starting to wonder if I inadvertently set that channel to AC-coupled for that trace. It is barely possible that I flipped the channel coupling switch the wrong way after checking the baseline at "ground" coupling. I am having a hard time believing I would do that, though, since I did check the trace several times.

Awww... does that mean my little PCB JT isn't OU after all? I'm crushed.

TK,

That would be my guess.  Its one of the hazards of doing late night 'scoposcopy...

PW

Offline TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #548 on: April 11, 2013, 06:20:09 PM »
Well, the first place I generally try to look, to explain any anomalous results, is for my own errors. Thanks for suggesting that I try to reproduce that trace. I'm still not convinced that I actually did that silly mistake, though, so I am going to keep on trying. My own preferred suspect is a DC balance/offset error in the scope's internal calibration. Still, if that were the explanation I should have been able to reproduce the trace.
It's a good thing that Lawrence's scope shows the channel coupling right on the screen; sometimes he has used AC coupling deliberately, but at least he won't be using it accidentally without any way to tell, like on my scope.

Offline ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #549 on: April 12, 2013, 02:55:38 AM »
Well, the first place I generally try to look, to explain any anomalous results, is for my own errors. Thanks for suggesting that I try to reproduce that trace. I'm still not convinced that I actually did that silly mistake, though, so I am going to keep on trying. My own preferred suspect is a DC balance/offset error in the scope's internal calibration. Still, if that were the explanation I should have been able to reproduce the trace.
It's a good thing that Lawrence's scope shows the channel coupling right on the screen; sometimes he has used AC coupling deliberately, but at least he won't be using it accidentally without any way to tell, like on my scope.
I value my Atten Scope more now.  Just repeated the Input Waveform capture on Board 80.  You can draw the zero axis yourself.  It definitely shows current crossing the axis.....

Offline picowatt

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Re: Is joule thief circuit gets overunity?
« Reply #550 on: April 12, 2013, 03:52:37 AM »
I value my Atten Scope more now.  Just repeated the Input Waveform capture on Board 80.  You can draw the zero axis yourself.  It definitely shows current crossing the axis.....

Lawrence,

Although your Board 80 input current trace does show some excursion above the zero ref line, overall, there is much more area under the zero ref line.  Everything under the zero ref line is current being drawn from the battery.  Looking at that board's input and output power captures demonstrates an efficiency of about 75 to 85%.

TK's reply 522 definitely looked like it was OU by a significant amount.  The apparent equal area above and below the zero ref line on the input current trace made me wonder, however, if he had inadvertantly switched to AC coupling.  Although the jury may still be out on that completely, it is the most likely explanation for that anamalous capture.

PW








Offline ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #551 on: April 12, 2013, 05:03:55 AM »
Lawrence,

Although your Board 80 input current trace does show some excursion above the zero ref line, overall, there is much more area under the zero ref line.  Everything under the zero ref line is current being drawn from the battery.  Looking at that board's input and output power captures demonstrates an efficiency of about 75 to 85%.

TK's reply 522 definitely looked like it was OU by a significant amount.  The apparent equal area above and below the zero ref line on the input current trace made me wonder, however, if he had inadvertantly switched to AC coupling.  Although the jury may still be out on that completely, it is the most likely explanation for that anamalous capture.

PW

I got 10 more boards from Mr. Zhou yesterday.  Six of them have similar characteristics as Board 80.  Two could not light up the LED. Two showed unusual behavior (Broad 107 and 113.)
 
Instead of returning them to Mr. ZHou as "reject", I shall keep them and work on them more.  We may be able to learn much more from such "unusual boards" as TK recommended.
 
Here, I shall show the Input Waveforms of the "usual boards".

Offline ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #552 on: April 12, 2013, 05:46:55 AM »
I did the DSO analysis on Board 80 again with the latest "correct" setting.
 
The negative Input Power is now taken to be Current drawn from the battery.  Thus the COP is now positive.
 
The COP is still 1.41.  The Average Output Power is still greater than then Average Input Power.
 
More research is worthwhile.

Offline ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #553 on: April 12, 2013, 06:14:01 AM »
Input and Output Waveforms for the unusual Board 107.
 

Offline ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #554 on: April 12, 2013, 06:16:14 AM »
Input and Output for the unusual Board 113