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Author Topic: Is joule thief circuit gets overunity?  (Read 600501 times)

Void

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Re: Is joule thief circuit gets overunity?
« Reply #960 on: June 01, 2013, 07:31:53 PM »
btw,what kind of voltages does one get on a average bakspike?

It varies widely depending on many factors such as the exact driving pulse shape, duty cycle, frequency, amplitude, inductance of the inductor, current drive capability of the pulse source, etc. The voltage amplitude of the generated back spike will also depend on any load that is connected to the inductor and the diode type used to capture the spike, etc. Any load connected can potentially greatly limit the amplitude of the back spike. Many factors involved.

profitis

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Re: Is joule thief circuit gets overunity?
« Reply #961 on: June 01, 2013, 09:57:23 PM »
@void yes caps r tricky due to fluctuating voltage/countervoltage,heat,leaks etc thats why i recomend bats,80percent efficiency conversion electro energy to chemical energy and vise versa.you take your now series charged load bats and swap in parallell to use as a source,throw away the single original(now flat) source and replace with same number of flat bats as the original load and from there it can be perpetual swaps,series to parallel,parallel to series,assuming overunity.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #962 on: June 02, 2013, 08:50:51 PM »
Something interesting. I haven't had a whole lot of time for testing in the last few weeks, but I conducted a few tests this morning with my proto-board joule thief circuit. This is very preliminary, and some further analysis would be required to try to determine what exactly is going on, but this is what I measured. I ran this test twice to try to eliminate inadvertent measurement error as a factor in the results. Ran tests on my JT circuit to compare circuit efficiency when powering the circuit with a regulated DC power supply set to 0.5VDC, as compared to powering the circuit with my 3000 Farad nominal value super capacitor charged to about 0.5VDC. My measured results in both test runs using the 2 channel scope data logging/instantaneous power/average power calculation method for input and output power, show the super cap powered JT circuit as giving about 6% to 7% or so increase in circuit efficiency. Input and output currents are a bit less when powering with the super cap, so that might account for the increased efficiency, but I am not sure. I would need to run more tests to see if this apparent increase in circuit efficiency is consistent over a number of test runs. This same sort of test could probably be run to compare a regulated DC power supply to an AA or AAA cell as well.

TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #963 on: June 02, 2013, 09:46:46 PM »
It's hard to know just how much the supply's regulation and filtering is affecting your measurements, though. Certainly you aren't going to be able to "recharge" your power supply from the JT circuit, as some people think happens with batteries! At low voltages, most bench supplies aren't going to perform as stably or cleanly as they do at higher voltages. There are ways to get around this by using external voltage dividers and heavy filtering, probably, but not many experimenters are likely to go to that much trouble to assure clean and precise low-voltage power.

Some experimenters have even been known to cite the power supply's own display meters, usually digital, for their voltage and current measurements. I kid you not.

profitis

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Re: Is joule thief circuit gets overunity?
« Reply #964 on: June 02, 2013, 11:49:00 PM »
@void,perhaps your regulated dc source is pulsing?if its from the mains.

profitis

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Re: Is joule thief circuit gets overunity?
« Reply #965 on: June 03, 2013, 12:18:13 AM »
this is completely offtopic but do any of you guys have any tantalum capacitors lying around?perhaps stuck on a old junk circuitboard?

ltseung888

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Re: Is joule thief circuit gets overunity?
« Reply #966 on: June 03, 2013, 12:43:03 AM »
Waveforms from a secondary coil on Board 135.  A 1 meter copper coil was wound around the toroid on Board 135.  A load of 50 ohm + 1 ohm was used.  The Secondary Coil Voltage was taken across the 51 ohms and the Secondary Coil Current was taken across the 1 ohm resistor.
 
The Secondary Coil gave much more flexibility.  Replacing the 50 ohm resistor with a variable resistor affects the current both on the Secondary Coil and that in the JT circuit.  Since the load is purely resistive in this case, the resulting power from this Secondary Coil is all positive.  This power happened to be more than that from the primary Output of the JT.  The sum gave a COP of 1.04 but that was at the range of experimental error of the Atten and the resistors.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #967 on: June 03, 2013, 03:51:56 AM »
It's hard to know just how much the supply's regulation and filtering is affecting your measurements, though. Certainly you aren't going to be able to "recharge" your power supply from the JT circuit, as some people think happens with batteries! At low voltages, most bench supplies aren't going to perform as stably or cleanly as they do at higher voltages. There are ways to get around this by using external voltage dividers and heavy filtering, probably, but not many experimenters are likely to go to that much trouble to assure clean and precise low-voltage power.

Some experimenters have even been known to cite the power supply's own display meters, usually digital, for their voltage and current measurements. I kid you not.

The thing is though that I use my scope to measure and monitor the input voltage, and when my power supply is set to 0.5VDC output, the voltage waveform is very stable. Very little fluctuation. For whatever reason, the super cap (when charged to close to the same voltage as the power supply ) was giving a measured increase in efficiency. I am going to run the test again, and I will post my scope screen shots in case anyone wants to compare the waveforms when using the power supply and when using the super cap as input power source. There is some difference in the waveforms.


TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #968 on: June 03, 2013, 04:04:33 AM »
this is completely offtopic but do any of you guys have any tantalum capacitors lying around?perhaps stuck on a old junk circuitboard?
I do, old and new. Why?

TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #969 on: June 03, 2013, 04:08:14 AM »
The thing is though that I use my scope to measure and monitor the input voltage, and when my power supply is set to 0.5VDC output, the voltage waveform is very stable. Very little fluctuation. For whatever reason, the super cap (when charged to close to the same voltage as the power supply ) was giving a measured increase in efficiency. I am going to run the test again, and I will post my scope screen shots in case anyone wants to compare the waveforms when using the power supply and when using the super cap as input power source. There is some difference in the waveforms.
Well, that's good, but of course you realize that your power supply already has a lot of filter capacitance in parallel with its output, probably, and chokes in series; it's just that the caps in the power supply have their charge constantly replenished from the voltage regulator.
Certainly there will be differences in things like impedance of the three power sources (bat, cap, psu) so why shouldn't waveforms and measured efficiencies differ a bit?

TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #970 on: June 03, 2013, 04:10:48 AM »
A 1 meter copper coil was wound around the toroid on Board 135.  A load of 50 ohm + 1 ohm was used.  The Secondary Coil Voltage was taken across the 51 ohms and the Secondary Coil Current was taken across the 1 ohm resistor.
 

Congratulations! You've invented the transformer!

(sorry, I couldn't resist.  ;)   )

Void

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Re: Is joule thief circuit gets overunity?
« Reply #971 on: June 03, 2013, 04:56:25 AM »
Well, that's good, but of course you realize that your power supply already has a lot of filter capacitance in parallel with its output, probably, and chokes in series; it's just that the caps in the power supply have their charge constantly replenished from the voltage regulator.
Certainly there will be differences in things like impedance of the three power sources (bat, cap, psu) so why shouldn't waveforms and measured efficiencies differ a bit?

Yes, there is no doubt that the joule thief circuit operation will be affected by what is connected to its power input terminals, but rather than having a higher efficiency with the regulated power supply connected, the measured efficiency is higher with the super cap connected, although the waveforms appear to be fairly similar overall. Although the input voltage is about the same, the circuit seems to draw less current with the super cap connected, and that might account for the higher efficiency, although I don't know exactly why that is. Perhaps the joule thief can draw more current with the power supply connected because of the better regulation. This just may indicate that a joule thief type circuit runs more efficiently as the input current draw is reduced, but again, I am not certain exactly why that would be.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #972 on: June 03, 2013, 05:05:05 AM »
Power and Efficiency of my Joule thief circuit powered with regulated DC power supply:
Input Voltage: 504mV
Input Power: 2.995mW
Output Power: 2.002mW
Efficiency: 66.84%

Scope shots are attached below.
Yellow traces are voltage, and blue traces are current.

Void

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Re: Is joule thief circuit gets overunity?
« Reply #973 on: June 03, 2013, 05:12:18 AM »
Power and Efficiency of my Joule thief circuit powered with my 3000 Farad Super cap:
Input Voltage: 500mV
Input Power: 2.501mW
Output Power: 1.947mW
Efficiency: 77.85%

That's an increase in circuit efficiency of about 11%. This is the exact same JT circuit as in the previous test I posted, with the only difference being that the input power is now being supplied by a super cap, charged to very close to the same voltage that the regulated power supply was set to in the previous test. Notice that the output power consumption of the LED is very close in both circuit arrangements, but the input current draw drops when using the super cap, thus reducing the input power a fair bit.

@Lawrence, this is just preliminary, but the tests I have run comparing JT circuit efficiency between using a regulated DC supply and using a super cap as the input power source would seem to lend support to your own tests where I think you were using a battery and a timer to intermittently charge a super cap, (or what was your exact setup?), and you noticed that it took longer for the battery to run down.

Scope shots are attached below.
Yellow traces are voltage, and blue traces are current.

TinselKoala

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Re: Is joule thief circuit gets overunity?
« Reply #974 on: June 03, 2013, 05:19:01 AM »
It would be interesting if you could equate the output impedances of the psu and the cap somehow, but I have no idea how to do this. It hardly seems fair to have to put a resistor in series with the supercap. It certainly looks like you are getting more ringing with the PSU, and this is a loss mechanism.