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Author Topic: Is joule thief circuit gets overunity?  (Read 600493 times)

Void

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Re: Is joule thief circuit gets overunity?
« Reply #825 on: May 13, 2013, 07:59:22 PM »
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.

That may possibly just be a characteristic of the discharge pattern of the type of rechargeable battery you are using. To see if that might be the case, you could set up a control test where you put maybe two rechargeable batteries in series with a LED and a resistor, and monitor the discharge pattern of the batteries this way as a comparison. You would want to choose a resistor value that limits the LED current to a comparable level to what your joule thief circuit runs at when the battery is fully charged. It won't be an exact comparison as in this case you would have two rechargeable batteries in series, but it might still be a valid comparison. Just an idea.



TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #826 on: May 13, 2013, 10:15:31 PM »
Yes, pretty much, if your time slices are equal in duration.
Really, you are using the spreadsheet to perform a numerical approximation of an integral. The instantaneous power value is multiplied by the "duration" or the interval to the next pair of samples. This gives a tall skinny rectangular area. Then all the areas are added together to approximate the actual area "under" the smooth instantaneous power curve. This is a numerical integration and the time durations of the individual rectangles can be variable, but should obviously be as small as possible. This corresponds to the total energy in Joules (Watts x Seconds) that pass your measuring point in the total time interval. Then you divide this value by the time in seconds and you get an average power value in Watts (Joules / second) for that entire interval.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #827 on: May 13, 2013, 10:48:13 PM »
Yes, pretty much, if your time slices are equal in duration.
Really, you are using the spreadsheet to perform a numerical approximation of an integral. The instantaneous power value is multiplied by the "duration" or the interval to the next pair of samples. This gives a tall skinny rectangular area. Then all the areas are added together to approximate the actual area "under" the smooth instantaneous power curve. This is a numerical integration and the time durations of the individual rectangles can be variable, but should obviously be as small as possible. This corresponds to the total energy in Joules (Watts x Seconds) that pass your measuring point in the total time interval. Then you divide this value by the time in seconds and you get an average power value in Watts (Joules / second) for that entire interval.

Ok, thanks. I will see if I can figure out how to do this with my scope, but the user manual for my scope is almost useless. I think I can figure out how to get the scope to log a channel's waveform data to a data file, but the manual doesn't explain how to set up to log both channels to a data file at the same time, nor how to start and stop data logging on demand. I will play around with it and see if I can figure it out. :)



ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #828 on: May 13, 2013, 11:31:13 PM »
Ok, thanks. I will see if I can figure out how to do this with my scope, but the user manual for my scope is almost useless. I think I can figure out how to get the scope to log a channel's waveform data to a data file, but the manual doesn't explain how to set up to log both channels to a data file at the same time, nor how to start and stop data logging on demand. I will play around with it and see if I can figure it out. :)

Does your scope have a USB that allows the capture/save of the CSV file?  If so, that CSV file should contain the Instantaneous Voltage and Current at the many sample points.

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #829 on: May 13, 2013, 11:56:39 PM »
Day 7 of the experiment.  LED on Board 116 OFF totally when checked at 8:30pm on Day 6.
 
LED on Board 124 still ON but dimly.  The experiment will be continued until the LED is OFF totally.
 
@TK
 
I am aware of my poor DSO skills.  That is why I sow seeds and let others do the "proper job".  One good happening is the poynt99 scope shots and the subsequent interest in getting the 4-CH Tektronics in Hong Kong.  I shall NOT be the owner but may have access to it with experts helping me.  So just consider my Atten Scope shots in the past, present and future as trash if you like.  For me, the lighting of the LED for 3 days with a rechargeable AA battery reading 0.352V and the spike waveforms is worth further research (especially by others with the resources and skills). 

Void

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Re: Is joule thief circuit gets overunity?
« Reply #830 on: May 14, 2013, 12:30:43 AM »

Does your scope have a USB that allows the capture/save of the CSV file?  If so, that CSV file should contain the Instantaneous Voltage and Current at the many sample points.

Yes, I think my scope is at least somewhat similar to your scope. I just need to experiment with it to see if I
can get everything to work OK. I may have to wait until the weekend to find time to try it though.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #831 on: May 14, 2013, 01:14:38 AM »
I am aware of my poor DSO skills.  That is why I sow seeds and let others do the "proper job".  One good happening is the poynt99 scope shots and the subsequent interest in getting the 4-CH Tektronics in Hong Kong.  I shall NOT be the owner but may have access to it with experts helping me.  So just consider my Atten Scope shots in the past, present and future as trash if you like.  For me, the lighting of the LED for 3 days with a rechargeable AA battery reading 0.352V and the spike waveforms is worth further research (especially by others with the resources and skills).

Hi Lawrence. I think you are doing fine, but just make sure your trigger level setting is always set below the lowest peaks of the waveform you are triggering on. The other issue to watch out for is that the smaller the current waveform amplitude gets (the more the current waveform amplitude gets closer to the noise level amplitude), the more the error in your current measurements will increase. In general once your current or voltage waveform amplitudes get close to the noise level (low mV amplitude) then you can't really rely on those measurements as being really accurate. Any tests you can do that keep the current and voltage waveforms a fair bit larger than the noise level will reduce error in your measurements.

Another thing that you can do is to have everything connected in your circuit including your scope probes, except have one of the input voltage power leads disconnected, and then take a scope screen shot of the noise level that your circuit and scope leads are picking up as a sort of a base line measurement. Take note of the Max + and - voltage readings on the noise. This will give you an idea of how much error noise can be contributing to your measurements. For example, if the noise maximum at noise peaks is +/- 5mV, and your waveform being measured is lets say 10 mV max, you could have very large errors in your measurements of this waveform.  Your signal to noise ratio is too low to make reasonably accurate measurements. You may already be aware of this, but just pointing it out anyway as no doubt if you present your circuit and experimental data to a university for review, they may quickly dismiss your measurements if some of the measurements are made with the waveform being too close to the noise level. Showing a scope screen shot of the noise level with all the probes and circuit components connected, except for one of the battery or capacitor power leads, establishes an approximate baseline for the noise level to help determine what the level of error in your measurements due to noise might be. Again, just another idea.

By the way, measuring very low signal levels is where the differential oscilloscope probe becomes very useful. This type of scope probe measures only the difference in signal voltage between its two leads, and any electrical noise that is picked  up and which is common to both of the leads on the differential probe gets ignored. For any tests that have to be done at very low waveform amplitudes, you may have to consider using differential probes if you want to have more reliable measurements. I am not sure if they are expensive or not, but if you use Tektronix probes then they are probably not cheap. :)


ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #832 on: May 14, 2013, 02:15:58 AM »
Hi Lawrence. I think you are doing fine, but just make sure your trigger level setting is always set below the lowest peaks of the waveform you are triggering on. The other issue to watch out for is that the smaller the current waveform amplitude gets (the more the current waveform amplitude gets closer to the noise level amplitude), the more the error in your current measurements will increase. In general once your current or voltage waveform amplitudes get close to the noise level (low mV amplitude) then you can't really rely on those measurements as being really accurate. Any tests you can do that keep the current and voltage waveforms a fair bit larger than the noise level will reduce error in your measurements.

Another thing that you can do is to have everything connected in your circuit including your scope probes, except have one of the input voltage power leads disconnected, and then take a scope screen shot of the noise level that your circuit and scope leads are picking up as a sort of a base line measurement. Take note of the Max + and - voltage readings on the noise. This will give you an idea of how much error noise can be contributing to your measurements. For example, if the noise maximum at noise peaks is +/- 5mV, and your waveform being measured is lets say 10 mV max, you could have very large errors in your measurements of this waveform.  Your signal to noise ratio is too low to make reasonably accurate measurements. You may already be aware of this, but just pointing it out anyway as no doubt if you present your circuit and experimental data to a university for review, they may quickly dismiss your measurements if some of the measurements are made with the waveform being too close to the noise level. Showing a scope screen shot of the noise level with all the probes and circuit components connected, except for one of the battery or capacitor power leads, establishes an approximate baseline for the noise level to help determine what the level of error in your measurements due to noise might be. Again, just another idea.

By the way, measuring very low signal levels is where the differential oscilloscope probe becomes very useful. This type of scope probe measures only the difference in signal voltage between its two leads, and any electrical noise that is picked  up and which is common to both of the leads on the differential probe gets ignored. For any tests that have to be done at very low waveform amplitudes, you may have to consider using differential probes if you want to have more reliable measurements. I am not sure if they are expensive or not, but if you use Tektronix probes then they are probably not cheap. :)

I now know why that the Lord chose me to sow the seeds.  I had two strokes, poor eyesight and hearing, shaky hands, cannot master the options on the mobile phone and unskilled at the DSO.  With someone more talents, there will be the temptation to "claim credit as ones work".  Once that temptation comes, one would hide the findings and try to develop products for one's benefit.
 
I do not mind showing the "bad and poor" results to any group.  The moment they look at the old man with slow reactions and faulty presentations, they know that they have to do the actual work themselves.  Some groups will automatically dismiss the entire lead-out energy concept.  But there are groups willing to give it a try.  Seed falls on fertile soil.
 
Thank you for all the good suggestions.  I am sure the groups getting the 4-CH Tektronics in Hong Kong will continue to monitor this thread and hopefully will develop products to benefit the World.
 
I am attaching the results for Board 119 with relatively high Input Voltage of 1.1V for your reference.

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #833 on: May 14, 2013, 02:30:23 AM »
@Void,
 
With the previous post diagrams and analysis, one can see that the use Vrms for analysis could be totally wrong.  For example, the COP calculated from
Output (Ch1 Vrms * Ch2 Vrms)/ Input (Ch1 Vrms *Ch2 Vrms) = 1.27.
 
The COP from EXCEL gives COP = -19.54.  The negative sign came from Input.
 
*** If you have a DC Power Supply, lower the Input Voltage to around 0.4V and see if you can observe the crossing of the 0 ref line and/or the spikes on both sides of the 0 ref line for Input Current.  If you do not have a DC Power Supply, find and drain a rechargeable AA battery to around that voltage and observe the waveform.

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #834 on: May 14, 2013, 04:29:35 PM »
Board 124 can no longer maintain continued lighting of LED.
 
LED was lighted only when the Battery was connected.

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #835 on: May 14, 2013, 04:56:35 PM »
The Atten may not be too bad after all.  The Offset problem may be due to not enough warm up time.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #836 on: May 14, 2013, 05:16:33 PM »
@Void,
 
With the previous post diagrams and analysis, one can see that the use Vrms for analysis could be totally wrong.  For example, the COP calculated from
Output (Ch1 Vrms * Ch2 Vrms)/ Input (Ch1 Vrms *Ch2 Vrms) = 1.27.
 
The COP from EXCEL gives COP = -19.54.  The negative sign came from Input.
 
*** If you have a DC Power Supply, lower the Input Voltage to around 0.4V and see if you can observe the crossing of the 0 ref line and/or the spikes on both sides of the 0 ref line for Input Current.  If you do not have a DC Power Supply, find and drain a rechargeable AA battery to around that voltage and observe the waveform.

Ok, that is interesting. However, something doesn't look right with your input current waveform. It is showing as mostly negative when it should be positive current pulses, at least for the most part. That could be where the problem is. Can you confirm that you had channel 2 set to DC coupling? It looks like the coupling was set to AC?

I believe the RMS readings will not be useable if your waveform is not completely positive (pulsating DC) or if the waveform has both positive and negative swings and the positive and negative swings are not very symmetrical. In the scope shots you posted it looks like you didn't have your channel 2 probe set to DC coupling when you measured the input current. If the current waveform were showing as pulsating DC (all positive), I think the RMS reading would provide you with a quite different result.

I did a quick test with the input voltage set at 0.4V, and I do not get much noticeable negative swing on the input or output current waveforms. The output current is starting to get down fairly close to the noise level at this input voltage however. I also tried setting the input voltage to 0.36V, and although my LED still glows dimly at this input voltage, the output current is just barely detectable as very tiny blips on the scope trace, so the output current is unmeasurable on my scope at this input voltage. The output current is right in the scope's noise level at this input voltage.
« Last Edit: May 14, 2013, 07:50:45 PM by Void »

Void

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Re: Is joule thief circuit gets overunity?
« Reply #837 on: May 14, 2013, 05:27:57 PM »
The Atten may not be too bad after all.  The Offset problem may be due to not enough warm up time.

Yes, if you find that letting your scope warm up for 20 minutes gives less offset then that is probably a good idea. After your scope has warmed up for twenty minutes you can then maybe try running the scope's self-calibration routine and see how everything looks then. You should connect each of your scope probe tips to your scope's ground lug connection when running your scope's self-calibration function.



TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #838 on: May 14, 2013, 07:38:27 PM »
Well, chalk that up to another item of scoposcopy that is as basic as using the "ON" switch to turn it on.

Allowing sufficient warmup time --- usually arbitrarily defined as at least 30 minutes  --- is a basic operational requirement for any instrumental measurements. We haven't mentioned it here before -- except that .99 did -- because it is so basic a concept. But in every text about making measurements, and in every scope manual I have ever seen (with the exception of the Atten) the proper warm-up time interval is mentioned, before making quantitative measurements or internal scope calibrations.

And "note bene"..... it was Rosemary Ainslie's practice, throughout her long series of measurements, to turn on her oscilloscope, make a quick measurement as soon as it booted up, then turn the scope off again, until she was ready to make another measurement.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #839 on: May 14, 2013, 08:42:46 PM »
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