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Author Topic: Is joule thief circuit gets overunity?  (Read 600293 times)

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #810 on: May 12, 2013, 10:08:50 AM »
Day 5 (Mother's Day) at 3:30pm.  LED on Board 116 is still ON.
 
@void
 
I can see that you are using the breadboard.  I stopped using the breadboard because the results from different breadboards by different individuals were very different.  In particular, we tried to place the hand over the board and the scope shots changed significantly.
 
For a fair comparison, please give me your snake mail address and I can send you two Zhou boards FREE.  The passing test for the Zhou board is "crossing the 0 ref line" on the Atten. 
 
The simplest test with the Zhou board at present is - just use a rechargeable AA battery as Input and hook up to Vin+ and Iout-.  (previous boards use A1+ and A4-)   Use a DMM to measure the voltage (also connected across Vin+ and Iout-).  The Voltage will drop from 1.4V to 0.4 volt in 2-3 days.  Then at around 0.4V, strange things start to happen.   The expectation is that it will die (LED OFF) within hours.
 
The experimental result will show that the LED will be ON dimly for at least 2 or more days.  The Input waveform will have spikes as shown.  Not all JT circuits will show such characteristics.  Only the Zhou Boards are "guaranteed to have such characteristics because if a board does not pass this test, it is NOT a Zhou Board.....
 
Welcome to this lead-0out energy research.  TK. PW and Poynt99 will teach you on how to use your DSO.  Each DSO is different and thus every one goes on a different learning curve.  The good thing at present is - I do not even need a DSO to show that a rechargeable AA battery reading 0.352V can light up the LED for days dimly (Board 116).  If I add a capacitor and a timer, a similar AA battery reading 1.317V at beginning can light up a similar LED brightly for a much longer time.
 
*** Poynt99 taught me three years ago NEVER to use the Vrms value for analysis.  The correct way is to use Instantaneous Power = Instantaneous Voltage x Instantaneous Current.
 
The experiment is still on-going.  More independent teams are welcome.  You can be one of them.....

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #811 on: May 12, 2013, 10:27:40 AM »
I tried another test with the exact same Joule Thief circuit that I used in my previous test (see me previous post above), except this time I placed a capacitor in parallel to the 1k ohm base resistor. I didn't have all that many capacitor values in the low nF range to try with, but I tried 100nF, 20nF, and 10nF. The 10nF nominal value (12.5nF measured value) capacitor seemed to give the highest efficiency of these three values. With the 12.5nF capacitor in parallel to the 1k ohm base resistor, efficiency increased to 95.2%, however the LED glows dimmer for about the same input voltage due to less current flowing in the circuit. At any rate, adding a parallel capacitor across the 1k ohm base resistor appears to have increased efficiency a fair bit with my circuit setup. Thanks Tinselkoala for the suggestion. If you compare the scope shots from the previous test to the scope shots from this new test, it appears that the parallel base capacitor limits the amplitude of the current spike peaks quite a bit, which for some reason seems to increase efficiency a fair bit. This also caused the frequency of oscillation to increase a fair bit as well. I am attaching the scope shots which I used to make the input and output measurements with the 12.5nF cap across the base resistor.

Average Input Power:
Vin = 510mV
Iin = 1.84mA
Input Power = 938uW

Average Output Power:
Vout = 921mV
Iout = 970uA
Output Power = 893uW

Efficiency = 893uW/938uW x 100 = 95.2%

- void -

In the scope shots below, yellow are the voltage traces, and green are the current traces.
@Void,
 
Please do what TK asks - include the resistors and probe connections in your circuit diagram.  Poynt99 has clearly explained that the current values should be negative for DSO analysis.  Your shots showed positive.  Did you use the Invert function?  If not, your shots may be measuring something totally different.  Please check.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #812 on: May 12, 2013, 07:31:15 PM »
@TinselKoala, @Lawrence:
A quick reply for the moment.
I am attaching a schematic which includes the placement of the two 1 ohm current sense resistors I used, as well as the scope probe leads placement I used to make my measurements.

Regarding my using the RMS measurement feature on my scope to make my voltage and current measurements for these tests, as I mentioned I am aware that using the RMS feature (equivalent to what a True RMS voltage meter does, I believe) is not the most accurate way to make measurements for input and output power with these types of waveforms. There are certainly limitations there, and I am aware of this.

From what I have observed, my scope appears to only use the positive portion of a waveform to do the RMS calculations (I am not certain of this, but the scope appears to do it this way), so if you have an AC waveform in which the positive and negative swings of the waveform are not really close to being symmetrical, then using the RMS feature is not going to give very accurate results at all. However, in my measurements here I observed that the waveforms were all pulsating DC (i.e. no negative swings to the waveforms for the most part) so I think my using RMS measurements here should give at least ballpark results. I agree that using this measurement technique for these type of waveforms is potentially not very accurate, so I would definitely want to confirm the measurements using a better measurement method before attempting to draw any definite conclusions. :) These tests I did so far were just preliminary to get an approximate idea of the efficiency of the circuit. I plan to do more careful measurements later.

I am quite familiar with the use of oscilloscopes, but my experience is fairly old school with basic analog scopes, so I will have to familiarize myself with using some of the other capabilities my DSO has, such as data logging and math and calculation features.
@TinselKoala, I will check what other calculation/math features my DSO has.
@Lawrence, I would like to take you up on your offer to run tests/measurements on your joule thief board. I will email you later today with my mailing address. Thank you.
@Lawrence, since I am using a 2 channel DSO and I measure the input and output power separately by moving the scope probes over, I can connect in my scope probes as shown in the attached schematic when measuring the input voltage and current, and there is no need to invert the current channel when attaching the scope probes this way, I believe. At any rate I was using RMS values to calculate the average input power, so if the input waveform was inverted it shouldn't matter when using the RMS value for the current (my waveform was pulsating DC). For instantaneous power measurements, I agree that it is important to make sure that no waveforms are inverted.

Thanks for the feedback guys!

- void -
« Last Edit: May 12, 2013, 10:35:56 PM by Void »

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #813 on: May 12, 2013, 10:52:00 PM »
@TinselKoala, @Lawrence:
A quick reply for the moment.
I am attaching a schematic which includes the placement of the two 1 ohm current sense resistors I used, as well as the scope probe leads placement I used to make my measurements.
*** Try to use the same circuit as mine.  My circuit will cater for both 2-CH and 4-Ch scopes.  It will also be a closer comparison.

Regarding my using the RMS measurement feature on my scope to make my voltage and current measurements for these tests, as I mentioned I am aware that using the RMS feature (equivalent to what a True RMS voltage meter does, I believe) is not the most accurate way to make measurements for input and output power with these types of waveforms. There are certainly limitations there, and I am aware of this.
*** Poynt99 will probably repeat his explanation once more or point you to the past posts


From what I have observed, my scope appears to only use the positive portion of a waveform to do the RMS calculations (I am not certain of this, but the scope appears to do it this way), so if you have an AC waveform in which the positive and negative swings of the waveform are not really close to being symmetrical, then using the RMS feature is not going to give very accurate results at all. However, in my measurements here I observed that the waveforms were all pulsating DC (i.e. no negative swings to the waveforms for the most part) so I think my using RMS measurements here should give at least ballpark results. I agree that using this measurement technique for these type of waveforms is potentially not very accurate, so I would definitely want to confirm the measurements using a better measurement method before attempting to draw any definite conclusions. :) These tests I did so far were just preliminary to get an approximate idea of the efficiency of the circuit. I plan to do more careful measurements later.

I am quite familiar with the use of oscilloscopes, but my experience is fairly old school with basic analog scopes, so I will have to familiarize myself with using some of the other capabilities my DSO has, such as data logging and math and calculation features.
*** Make sure that you are 100% efficient and confident on the EXCEL analysis of the captured results.  The captured results will reproduce the displayed waveforms and much more.
 
@TinselKoala, I will check what other calculation/math features my DSO has.
@Lawrence, I would like to take you up on your offer to run tests/measurements on your joule thief board. I will email you later today with my mailing address. Thank you.
@Lawrence, since I am using a 2 channel DSO and I measure the input and output power separately by moving the scope probes over, I can connect in my scope probes as shown in the attached schematic when measuring the input voltage and current, and there is no need to invert the current channel when attaching the scope probes this way, I believe. At any rate I was using RMS values to calculate the average input power, so if the input waveform was inverted it shouldn't matter when using the RMS value for the current (my waveform was pulsating DC). For instantaneous power measurements, I agree that it is important to make sure that no waveforms are inverted.
*** Please continue your experiments with the Board you built.  I shall send you Board 118 and Board 119.  The test result for these two boards will be posted here first with all test details.  Please pay special attention to the test results of these two boards.  Raise any questions or doubts.  Once you receive them, you can repeat the tests and compare them with your own boards.

Thanks for the feedback guys!

- void -

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #814 on: May 12, 2013, 11:11:17 PM »
Day 6 results on Board 116.  LED still ON dimly.
 
LED on Board 124 still ON brightly (but not as bright as beginning of Day 1).

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #815 on: May 12, 2013, 11:20:43 PM »
@Lawrence: How can you be absolutely sure that your timer device is not supplying any power at all to your circuit under test? How can you be sure that you have indeed accounted for all power inputs to your circuit? As I've shown, the circuit you and void and I are using is capable of picking up power from the environment very easily, and can produce bright light in the LED without even being connected to anything with any wires at all, if there's sufficient ambient power floating around. And power supplies and instrument probe leads can trick you by supplying power through ground loops and other wiring infecilities.
@TK,
 
Try to do the Board 116 experiment with a rechargeable AA battery.  The voltage of the battery should run down to approximately 0.4V and then remain there for a few days.  Capture the Input Waveform then and see if your waveforms show the spikes crossing the 0 reference line.
 
The experiment is simple enough - no capacitors and no twin timers to confuse the issue.
 

 
You can then eliminate the various other effect at your site.  If you prefer, I shall be happy to send you two Zhou boards just like with void.  More independent confirmation, the better.

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #816 on: May 12, 2013, 11:36:35 PM »
Spreadsheet comparison of Board 116 and Board 124.
 
LED on Board 124 is still very bright even in day time or with other lights on.  Board 116 is dim but is still ON - turn off other lights and the effect is unmistakable.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #817 on: May 12, 2013, 11:57:19 PM »
One of the main potential problems I see already when making measurements at low supply input voltages (for example at Vin < 0.5V), is the current magnitudes start to go down much closer into the noise levels. This can no doubt skew measurements and introduce a degree of error into the measurements results. However, it seems you say that you start to see the unusual results at these lower input voltages so we will have to take noise levels into account as best we can.

There is a technique of using a differential probe (or using two matched and calibrated probes) to take more accurate measurements at lower magnitude levels, but I have not used this method before so I am not familiar with the details. That may be a measurement method that might possibly improve measurement accuracy at lower input voltages, so it may be worth looking into. I am not certain that the differential probe measurement method would help here, but I think that it may. However if you are sending your boards to some universities for testing, they would probably be familiar with the differential probe measurement technique, and would likely use that method if it will give more accurate measurements.

- void -
« Last Edit: May 13, 2013, 08:39:12 AM by Void »

Void

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Re: Is joule thief circuit gets overunity?
« Reply #818 on: May 13, 2013, 12:02:10 AM »
Spreadsheet comparison of Board 116 and Board 124.
 
LED on Board 124 is still very bright even in day time or with other lights on.  Board 116 is dim but is still ON - turn off other lights and the effect is unmistakable.

Those are interesting test results. Definitely worth investigating further, IMO.

- void -

Void

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Re: Is joule thief circuit gets overunity?
« Reply #819 on: May 13, 2013, 02:26:58 AM »
@Lawrence. Here's an overview on using a differential oscilloscope probe when making low power measurements with a scope. The author of the article also recommends a current probe for low power current measurements as well.
http://www.edn.com/electronics-blogs/scope-guru-on-signal-integrity/4403528/Low-power-measurement-techniques

However, any testing I am going to do will just be with regular single-ended scope probes, so I will have to work within those limitations with the understanding that the margin of error will be higher. I do have a current probe for my scope, but it is cheaper quality one and it has poor shielding and is very susceptible to EM fields. I don't find it is any much more accurate than my regular scope probes.


ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #820 on: May 13, 2013, 06:39:55 AM »
@Lawrence. Here's an overview on using a differential oscilloscope probe when making low power measurements with a scope. The author of the article also recommends a current probe for low power current measurements as well.
http://www.edn.com/electronics-blogs/scope-guru-on-signal-integrity/4403528/Low-power-measurement-techniques

However, any testing I am going to do will just be with regular single-ended scope probes, so I will have to work within those limitations with the understanding that the margin of error will be higher. I do have a current probe for my scope, but it is cheaper quality one and it has poor shielding and is very susceptible to EM fields. I don't find it is any much more accurate than my regular scope probes.

Do not worry about the low current/power input for now.  We can always use the 2n3055 and much higher Input Voltage such as 12V Car batteries.  The load can easily be 1,000 LEDs.  The present experiment is to iron out the bugs and do simple proof of concept.

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #821 on: May 13, 2013, 07:08:25 AM »
It looks like the use of rechargeable batteries for Board 116 or similar makes a difference in battery life (or LED lighting time).
 
After the batterry hits the 0.4V mark, the LED with rechargeable battery continued for at least 3 days.  The LED with normal batteries died within 12 hours.  I now have 8 rechargeable AA batteries to try.

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #822 on: May 13, 2013, 10:03:16 AM »
Board 119 results posted here first.  The Board will be sent to void for verification after all tests are done.  The process will guarantee to have at least one independent verification.

TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #823 on: May 13, 2013, 03:08:47 PM »
1. Your trigger is set out of the range of your signal on CH1. This means that your scope will not be triggering accurately on some known and consistent portion of the signal waveform. This may be the root cause of the frequency error, or that error may be independent of trigger setting.
2. Your scope is reporting values that do not correspond to the trace indications, as I have noted in the diagram below. The discrepancy is most marked in the frequency error.
3. The "average" value of "zero" for the current trace is clearly incorrect, does not agree with the trace position, and most importantly IS SMALLER THAN THE KNOWN VOLTAGE ERRORS of your oscilloscope. This entire trace does not represent data at all; it is impossible to know, with your equipment as shown, whether it is noise, or represents a + 3 mV or a -3 mV true average. It looks to me like the trace is indicating about -2 mV average, but as I said, this is an unreliable measurement, beneath the noise and accuracy floors of the instrument, and thus meaningless.

Lawrence, the combination of your low level of scoposcopy skills and your inaccurate Atten scopes results in a lot of wasted time and effort, for yourself and everyone else interested in your work. Please put those miserable Atten oscilloscopes on a high shelf and refrain from using them in attempts to claim "overunity" or high COP results. Also, you might like to do a little bit of homework on the use and abuse of oscilloscopes. There are many good references, university lab class lecture notes, YouTube tutorials, and other sources of information on the use of scopes to make measurements, and how to avoid the pitfalls that have already entrapped you many times over.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #824 on: May 13, 2013, 07:09:08 PM »
1. Your trigger is set out of the range of your signal on CH1. This means that your scope will not be triggering accurately on some known and consistent portion of the signal waveform. This may be the root cause of the frequency error, or that error may be independent of trigger setting.
2. Your scope is reporting values that do not correspond to the trace indications, as I have noted in the diagram below. The discrepancy is most marked in the frequency error.

I find the frequency determination routines in these type of scopes is not very reliable over all. In the scope shots I posted previously for my second test the frequency readings were all over the place. When I want to get a frequency reading from my scope I usually just determine the waveform period myself from the scope trace and then determine the frequency that way. I have found that the frequency reading calculations my scope does are usually not very reliable unless you have fairly simple and clean waveforms. As far as Lawrence's other readings being off, that may be because of the trigger setting being off and/or because the signal is quite a bit in the noise level, and this may be throwing off the scope's auto measurements.

@Lawrence, if there is a way that you can run these same tests at higher input voltages so that your signal to noise ratio is higher, then your measurements should be a lot less prone to error.

@Tinselkoala, it seems my scope does not have a waveform integration feature. The user manual is pretty poor however, but it seems my scope does not have that feature. It may be only higher end scopes that have that feature? I think the best method for trying to determine power with the type of DSO I have would be to log the voltage and current data points to a file and then do the instantaneous power calculations in Excel like Lawrence is doing now.

@Tinselkoala, @Lawrence:
Is the method used to determine the average power from the data points, to calculate the instantaneous power for each voltage/current data point set, and then take the average of all the calculated instantaneous data points by summing all the calculated instantaneous power values and dividing by the number of data points? Or is there more to it than that?
Is this method considered to be a fairly accurate way (within the accuracy limitation of the scope) to determine average power?

- void -

« Last Edit: May 14, 2013, 12:33:44 AM by Void »