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Author Topic: Is joule thief circuit gets overunity?  (Read 600438 times)

Pirate88179

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Re: Is joule thief circuit gets overunity?
« Reply #1020 on: June 07, 2013, 03:10:06 AM »
That's an interesting idea. The coil windings will probably induce eddy currents in the metal casing of the batteries, which will probably reduce the self inductance of the windings, but it will be interesting to see what results this produces. Also, winding around the super cap should be interesting as well. Good idea! I will give this a try when I get a chance.

So will I.  Thanks TK.

Bill

Void

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Re: Is joule thief circuit gets overunity?
« Reply #1021 on: June 09, 2013, 05:49:58 AM »
@Lawrence: I was going to do some measurements on your boards using your method to connect the scope probes for the input voltage and current measurements, but I believe there is a problem with this method of measuring the input waveforms. When the scope probes are connected in the way you are doing it for the input waveform measurements, what you are measuring as Vin is actually not Vin, but actually Vin minus the voltage across the 1 ohm current sense series resistor. Although the voltage across the series resistor is not really high compared to the input voltage, based on my measurements it will make the input voltage measurement vary by about 4% or so. Since the accuracy of the scope itself when measuring such lower amplitude voltages is probably already not really great, adding an additional variation of about 4% to the input voltage measurements is probably too much error.

On another note, something odd I have been noticing recently:
I have been conducting a few tests with the JT circuits over the last few days, and something odd I have noticed in measurements with both your JT board #119 and my JT circuit is that sometimes I am measuring a somewhat higher efficiency on these JT boards than other times. (From tests so far, this variation seems to be on top of the difference in efficiency that I measured when comparing efficiency between a regulated DC supply and a super cap as power input sources, but I still need to run more tests to confirm that). I will run some tests on my scope to try to determine if my scope or probes could be having issues. I don't think my scope or probes are having issues, however I won't know for sure until I run some measurement tests with my scope. If the issue is not with my scope or probes, then I can't see why the efficiency of the JT boards could change every now and then. I am talking about differences in measured efficiency of 5% to 10% or so. The actual voltage and current waveform traces on the scope reflect these measured changes, so it doesn't appear to be a problem with the scope data logging. I know bad connections on the boards could also potentially cause something like this, but so far I have seen this variation on both my circuit and on Lawrence's board 119 which is soldered. I will check out the boards as well to see if I can rule out potential bad connections. Lawrence I won't post up any more measurements until I get a chance to investigate these odd measurement variations more carefully. Hope it's not an issue with my scope...  :)

Edit: The reason I think it is not an issue with my scope is because when I connect the Ch1 and Ch2 scope probes up to the scope's reference 1kHZ squarewave terminal, everything looks fine.






Void

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Re: Is joule thief circuit gets overunity?
« Reply #1022 on: June 09, 2013, 06:43:15 PM »
<deleted - poynt99 has already answered my question>

poynt99

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Re: Is joule thief circuit gets overunity?
« Reply #1023 on: June 09, 2013, 06:58:13 PM »
Void,

Yes, this is the way Lawrence and I measured his input power.

I already pointed out this issue some time ago in this thread, and Lawrence simply compensates for the CSR in the spreadsheet calculations. It makes the input power appear to be a little lower than it actually is.

There is no need to worry however, as all measurements have shown far less than unity, even without compensating for the CSR error.

The way you are measuring the LED power, you have the same problem there too.

poynt99

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Re: Is joule thief circuit gets overunity?
« Reply #1024 on: June 09, 2013, 07:19:37 PM »
Here is where I made that post:
http://www.overunity.com/12686/is-joule-thief-circuit-gets-overunity/msg356492/#msg356492

Void, Why are you OK with your Pout measurement when the very same issue is present?

Void

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Re: Is joule thief circuit gets overunity?
« Reply #1025 on: June 09, 2013, 07:30:21 PM »
Void,

Yes, this is the way Lawrence and I measured his input power.

I already pointed out this issue some time ago in this thread, and Lawrence simply compensates for the CSR in the spreadsheet calculations. It makes the input power appear to be a little lower than it actually is.

There is no need to worry however, as all measurements have shown far less than unity, even without compensating for the CSR error.

The way you are measuring the LED power, you have the same problem there too.

Hi poynt99. Ok, I wasn't aware that Lawrence was taking steps to try to compensate for that in his calculations. As long as he is compensating for that correctly then I guess it should work out ok in the wash. Thanks for the info on that. This is not a problem with the way I measure the output power, since we actually want to measure the total output power of the load (power dissipated by both the LED and the 1 ohm series resistor). In the case of the total load (LED and the one ohm resistor) the voltage drops across the LED and resistor are additive, which is what we want. So the power measurements for the load are correct.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #1026 on: June 09, 2013, 07:31:58 PM »
Here is where I made that post:
http://www.overunity.com/12686/is-joule-thief-circuit-gets-overunity/msg356492/#msg356492

Void, Why are you OK with your Pout measurement when the very same issue is present?

It's not the same issue. See my reply above...

poynt99

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Re: Is joule thief circuit gets overunity?
« Reply #1027 on: June 09, 2013, 07:52:12 PM »
Sure,

If you want to include the output CSR as part of the load. But none of us have done that to this point. We have considered the LED as the load.

If you want to go along that line of thinking (where the CSR is taken as part of the load), then you should be measuring and accounting for ALL the components in the circuit and consider them as an "output", excluding the battery of course.

Technically speaking (I know you hate that phrase), ALL the components excluding the battery are "output" components. The idea and hope is that one of these output devices gets most of the power. In this case, that component is the LED (which btw DOES get most of the power).

If anything, you should be more concerned about including the power in the input CSR vs. the output CSR, as the input CSR dissipates far more power than the output CSR. 

And don't forget the transistor, it has the second highest power dissipation in the circuit.

So you have a choice, either you call the LED the "load", or every component except the battery, the combined total "load".

Void

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Re: Is joule thief circuit gets overunity?
« Reply #1028 on: June 09, 2013, 08:30:01 PM »
Sure,

If you want to include the output CSR as part of the load. But none of us have done that to this point. We have considered the LED as the load.

If you want to go along that line of thinking (where the CSR is taken as part of the load), then you should be measuring and accounting for ALL the components in the circuit and consider them as an "output", excluding the battery of course.

Technically speaking (I know you hate that phrase), ALL the components excluding the battery are "output" components. The idea and hope is that one of these output devices gets most of the power. In this case, that component is the LED (which btw DOES get most of the power).

If anything, you should be more concerned with the power in the input CSR vs. the output CSR, as the input CSR dissipates far more power than the output CSR.

From the diagram I have of Lawrence's scope probe connection method (from Feb 2013), he seems to be measuring the output power the same way I am, unless he changed the way he is measuring it since February 2013.  At any rate, measuring power dissipation across the entire load is what we want here. Regarding the efficiency measurements, what is being measured is the overall circuit efficiency, and so it is understood that power dissipation by circuit components impacts the overall circuit efficiency.  Sure, the power dissipation by the one ohm current sense resistor in the input circuit skews measurements a bit as well, but unless someone has a really good quality current probe to use to measure the input current, then we don't really have a choice to not use this resistor. It's a good point though. It might actually be more accurate then not to compensate for the voltage drop across this input current sense resistor, since it would be more accurate to subtract the power dissipated by this resistor from the input power for circuit efficiency calculation. :) However, as you mentioned, if the measured circuit efficiency is not within a few percent of 100% then this measurement difference is probably not too critical. If I do ever measure efficiencies close to 100%, I would certainly want to move to a much higher quality scope to improve on measurement accuracy, as the error with the scope I have now may possibly be as much as +/- 5% at these low voltage and current magnitudes (hopefully the error in my scope measurements is not more than that) :).

poynt99

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Re: Is joule thief circuit gets overunity?
« Reply #1029 on: June 09, 2013, 08:38:40 PM »
As a rule of thumb when measuring the input and "output" power of a device, unless the chosen output component (LED in this case) power is easily exceeding the measured input power, one must individually-measure ALL the circuit components (excluding the source) and sum them all to compare to the input power.

If the sum total of all the output components' power is greater than the input power, then you may have something.

In the case of Lawrence's JT, the input power "Pin" is the source or battery power.

Each "output" component to be measured for power is listed below:

1) Input CSR resistor
2) 1k base resistor
3) base inductor resistance
4) collector inductor resistance
5) transistor
6) LED
7) output CSR resistor

If (P1+P2+P3+P4+P5+P6+P7) > Pin, then  ;D

If (P1+P2+P3+P4+P5+P6+P7) </= Pin, then  8)

Void

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Re: Is joule thief circuit gets overunity?
« Reply #1030 on: June 09, 2013, 09:03:27 PM »
As a rule of thumb when measuring the input and "output" power of a device, unless the chosen output component (LED in this case) power is easily exceeding the measured input power, one must individually-measure ALL the circuit components (excluding the source) and sum them all to compare to the input power.

If the sum total of all the output components' power is greater than the input power, then you may have something.

In the case of Lawrence's JT, the input power is the source or battery power.

Each "output" component to be measured for power is listed below:

1) Input CSR resistor
2) 1k base resistor
3) base inductor resistance
4) collector inductor resistance
5) transistor
6) LED
7) output CSR

If (P1+P2+P3+P4+P5+P6+P7) > Pin, then  ;D

If (P1+P2+P3+P4+P5+P6+P7) </= Pin, then  8)

Yes, that's true. When looking for over unity, the power dissipated by all the circuit components plus the power dissipated by the load is the total power consumed, but practically we really want to know what overall efficiency we can get with respect to the output load power, since the load power is the useable power, although a really inefficient circuit could maybe be used to help warm a room in the winter, or to power a peltier module. :) Actually, these days where battery life in mobile devices is quite important, I wonder if any manufacturers have started using peltier modules to convert heat produced by the circuitry back to electricity? Maybe the efficiency gains involved wouldn't make it worth the extra component cost however.


Void

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Re: Is joule thief circuit gets overunity?
« Reply #1031 on: June 09, 2013, 10:27:39 PM »
@Lawrence: Here are my measurements for your board #119, using your scope probe measurement method.
I didn't compensate for the voltage drop across the one ohm current sensing resistor at the input in my Excel calculations, but you can do that if you wish by modifying the attached Excel file. I am still seeing that odd variation in my efficiency measurements, and I am still investigating to see if I can figure out what might be causing it, so all I can say for now is this is what I measured for your board # 119 right at the current moment. :)

Input Voltage: 0.5VDC regulated supply
Input Power:   5.195mW
Output Power: 4.159mW
Efficiency:       80.06%

Scope screen shots and Excel files used for power calculations are attached.
Yellow traces are voltage and blue traces are current.
Input current waveform is inverted.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #1032 on: June 09, 2013, 11:04:46 PM »
@Lawrence: Here are my measurements for your board #118, using your scope probe measurement method.

Input Voltage: 0.5VDC regulated supply
Input Power:   4.893mW
Output Power: 3.765mW
Efficiency:       76.95%

Scope screen shots and Excel files used for power calculations are attached.
Yellow traces are voltage and blue traces are current.
Input current waveform is inverted.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #1033 on: June 10, 2013, 12:02:11 AM »
@Lawrence: Here are my measurements for your board #134, using your scope probe measurement method.
The other three boards you sent me do not light up. I would need to take a look at them to see what the issue is.

Input Voltage: 0.5VDC regulated supply
Input Power:   4.994mW
Output Power: 4.023mW
Efficiency:       80.56%

Scope screen shots and Excel files used for power calculations are attached.
Yellow traces are voltage and blue traces are current.
Input current waveform is inverted.

TinselKoala

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