LTJT - poynt99 Tests #2

[lanenal]

This is getting more and more interesting...if we are willing to put aside our prejudice, this is a great learning experience.

[feynman]

@PhysicsProf

Replacing the joule thief LED with a variable resistor was  an excellent idea.  Does modulating this resistor value change the resonant frequency significantly?

Looking forward to replicating.

[PhysicsProf]

@PhysicsProf

Replacing the joule thief LED with a variable resistor was  an excellent idea.  Does modulating this resistor value change the resonant frequency significantly?

Looking forward to replicating.

Yes, the resonant frequency is sensitive to the resistance of Rout, and the toroid windings (and L) and the input voltage -- and the choice of transistor.  The parameter space is quite large actually.

Glad you are joining in with real experiments, feynman.

[ion]

For those serious about the fine points of energy measurement, efficiency, and switching power supply design, may I suggest you go to Power Integrations:

http://www.powerint.com/

http://www.powerint.com/en/pi-university

Sign up and go to their on line university. Read all of their application notes, especially on the design of inductor and transformers for high efficiency . They have some interesting chips with very clever internals. Study them. They are a long way from a JT design, however, some of the principles may apply, and there is a huge body of knowledge here that will help you get up the learning curve faster.

[feynman]

@PhysicsProf

Would you say this image is an accurate comparison of waveforms?  I used your COP=0.90 circuit vs the COP=1.13 circuit and essentially photoshopped the images for comparison. 


http://feynmanslab.com/images/post4/PhysicsProf_comparison1_png.png

Thanks

[PhysicsProf]

@PhysicsProf

Would you say this image is an accurate comparison of waveforms?  I used your COP=0.90 circuit vs the COP=1.13 circuit and essentially photoshopped the images for comparison. 


http://feynmanslab.com/images/post4/PhysicsProf_comparison1_png.png

Thanks

Yes, that's the right identification -- and useful as long as one is careful to note that the scale for the lower-left (input) power waveform is 20 mv*V, whereas the scale for the lower-right (output) power waveform is 50 mV*V, so that must be taken into account.  Thanks.

[acmefixer]

I don't know what "IO" is.  The basis behind the statement is that an inductor can only put out as much energy as you put into it.  It's a device that can store energy and then release that stored energy.  It cannot create energy or harvest energy from "somewhere else."

[snip]

MileHigh

Well, the inductor can 'harvest' energy inadvertently when it is being exposed to an external magnetic field.  The result is that some energy is induced into the inductor and into the circuit it's in.  It acts as a magnetic pickup.  The toroid typically used in a JT is relatively immune because it has a closed tight magnetic path.  If it was a bobbin inductor like a typical choke it could pick up much more energy from external magnetic fields.

Here is my comments on my blog about this thread. http://watsonseblog.blogspot.com/2011/03/2011-mar-8-joule-thief-efficiency-113.html One thing I would really appreciate is a good closeup picture of the circuit.  It would make it a lot easier to replicate not only the circuit but the results.

[PhysicsProf]

Well, the inductor can 'harvest' energy inadvertently when it is being exposed to an external magnetic field.  The result is that some energy is induced into the inductor and into the circuit it's in.  It acts as a magnetic pickup.  The toroid typically used in a JT is relatively immune because it has a closed tight magnetic path.  If it was a bobbin inductor like a typical choke it could pick up much more energy from external magnetic fields.

Here is my comments on my blog about this thread. http://watsonseblog.blogspot.com/2011/03/2011-mar-8-joule-thief-efficiency-113.html One thing I would really appreciate is a good closeup picture of the circuit.  It would make it a lot easier to replicate not only the circuit but the results.

Attached find a photo acquired at the University on 4 March 2011, the day the n = 1.13 value was obtained as explained in some detail above.  The photo was taken with my HP digital camera, which is not great for close-up shots, but by comparing with the schematic (also in the attached), I think you can pick out the essential elements.  For these tests, I used a power supply as described rather than a battery, and found that varying the input voltage was useful in changing the conditions of the experiment.  The best results were obtained at 0.996V input voltage.  Note that the power IN and power OUT are measured and compared, so the use of a power supply should not mitigate against the validity of the calculated N.

[PhysicsProf]

.99 wrote:

I've discovered the error in my test setup (scope grounds on wrong node), so here are the measurements again, as pertaining to "schema02", i.e. no CSR3 present.

Pitotal = -46.64mW
Pcsr1 = 2.79mW
Pvbat = 49.43mW [Note that you can obtain this value directly when measuring Pitotal just by inverting the CSR1 channel]

Pototal = 33.62mW (PLED and Pcsr2)
Pototal + Pcsr1 = 36.41mW

I did not measure PQ.

So, efficiency not including output power dissipated in Q is:

n = 36.41mW / 49.43mW
n = 73.66%

.99

Would you say that I made the same error?  (See previous post showing connections used and photo showing probe connections to determine Pinput.)  Thanks.

[feynman]

Where are your two scope grounds connected again?

It almost looks like one scope ground is attached to the same place as the other scope probe?  Is that incorrect?

If you describe the photograph verbally in detail I will label the probes and grounds in Photoshop.

[PhysicsProf]

Where are your two scope grounds connected again?

It almost looks like one scope ground is attached to the same place as the other scope probe?  Is that incorrect?

If you describe the photograph verbally in detail I will label the probes and grounds in Photoshop.

In fact -- the two scope grounds (one under the other, but connected together) are connected at the same location as shown in the schematic, "north" of the 1 ohm CSR.  
The scope probes are then connected at points V1 and V2 shown in the schematic.
The larger cables coming in from the right are from the power supply, connected also as shown in the schematic.

Because of the location of the scope grounds the CSR1 voltage (V2) appears as negative, as expected from the schematic, whereas V1 and V3 appear as positive (generally -- the exception being the out-of-phase condition I have described).  Therefore, Pin (V1*V2) and Pout (V3*V2) appear as negative  (generally -- the exception being the out-of-phase condition I have described earlier in the thread).

[poynt99]

.99 wrote:
Would you say that I made the same error?  (See previous post showing connections used and photo showing probe connections to determine Pinput.)  Thanks.

From what I can tell professor, your scope grounds are connected correctly, esp. if they are connected as per my schematic. A quick check is to take note that your scope grounds are NOT connected to the battery negative terminal directly. They need to be connected to the other side of CSR1, which I believe you actually have done.

.99

[feynman]

No -- the two scope grounds (one under the other, but connected together) are connected at the same location as shown in the schematic, "north" of the 1 ohm CSR.  
The scope probes are then connected at points V1 and V2 shown in the schematic.
The larger cables coming in from the right are from the power supply, connected also as shown in the schematic.

Because of the location of the scope grounds, if a battery were used, the CSR1 voltage and the power appear as negative, as expected from the schematic.

Okay , sorry this is confusing.   So, as I understand:



-The red and the black leads on the right of the picture are the power supply.
-Both scope grounds are connected together .  They are connected to  CSR1 on the 'far' (away) side of the (-) of the power supply, labeled P11G and P12G in the schematic.  P21G is also connected here.  This ground is common across all calculated scope channels.

-This leaves us with three remaining scope probes (V1, V2, and V3).  And V4 which is the same as V2.

-V1 (for measuring input power) is connected to the (+) of the power supply .  [aka. P11T]
-V2 (for measuring input power) is connected to the (-) of the power supply, on the power supply side of CSR1. [aka. P12T]
-V3 (for measuring output power) is connected to the (+) of the LED, aka. the collector of the 2N2222 NPN transistor. [aka. P21T]
-V4 (for measuring output power) is the same waveform as probe V2.

Power_in = MEAN(V1*V2).  Aka the total power of the battery and CSR1 together. Aka Pitotal.
Power_out = MEAN(V3*V2) Aka the total power of the LED and transistor together.  Aka Pototal.

Is this correct?   Does any one else have an opinion on these methods?

Also PhysicsProf , did you get a chance to check the COP range of the 1K variable resistor which replaced the LED?

Thanks
-Feynman

[PhysicsProf]

From what I can tell professor, your scope grounds are connected correctly, esp. if they are connected as per my schematic. A quick check is to take note that your scope grounds are NOT connected to the battery negative terminal directly. They need to be connected to the other side of CSR1, which I believe you actually have done.

.99

This is correct.  Thank you, .99.

[PhysicsProf]

Okay , sorry this is confusing.   So, as I understand:



-The red and the black leads on the right of the picture are the power supply.
-Both scope grounds are connected together .  They are connected to  CSR1 on the 'far' (away) side of the (-) of the power supply, labeled P11G and P12G in the schematic.  P21G is also connected here.  This ground is common across all calculated scope channels.

-This leaves us with three remaining scope probes (V1, V2, and V3).  And V4 which is the same as V2.

-V1 (for measuring input power) is connected to the (+) of the power supply .  [aka. P11T]
-V2 (for measuring input power) is connected to the (-) of the power supply, on the power supply side of CSR1. [aka. P12T]
-V3 (for measuring output power) is connected to the (+) of the LED, aka. the collector of the 2N2222 NPN transistor. [aka. P21T]
-V4 (for measuring output power) is the same waveform as probe V2.

Power_in = MEAN(V1*V2).  Aka the total power of the battery and CSR1 together. Aka Pitotal.
Power_out = MEAN(V3*V2) Aka the total power of the LED and transistor together.  Aka Pototal.

Is this correct?   Does any one else have an opinion on these methods?

Also PhysicsProf , did you get a chance to check the COP range of the 1K variable resistor which replaced the LED?

Thanks
-Feynman

Yes, you have stated it correctly, Feynman -- and .99.

Feynman:

Also PhysicsProf , did you get a chance to check the COP range of the 1K variable resistor which replaced the LED?

  Not yet -- I have not made the trip back to the University since the tests last Friday, March 4th, reported on above.

[exnihiloest]

Hi poynt99

Is the output power measurement done using the product of rms voltage values, or by integrating over time the product of the instantaneous values V2(t)*V3(t)?
Only the second method can give correct results. The first one is false because the rms value of a product is not equal to the product of rms values.

May be I missed something. Could you clarify?

[poynt99]

Hi poynt99

Is the output power measurement done using the product of rms voltage values, or by integrating over time the product of the instantaneous values V2(t)*V3(t)?
Only the second method can give correct results. The first one is false because the rms value of a product is not equal to the product of rms values.

May be I missed something. Could you clarify?

We are using neither, but closer to the energy measurement you mention above.

We have been simply measuring input and output power using v(t) and i(t). It is the same result as the energy measurement, because the JT oscillation is periodic.

We've previously established the protocols for measurement, and all agreed that measuring the power is adequate and equivalent in this case. I hope you are not suggesting the contrary. It was also established long ago with Lawrence, that using RMS values is incorrect.

.99

[feynman]

@exnihiloest

Lanenal developed the energy test method, so I'm sure he can comment on details.  

I use an old analog scope, so I don't have a scope with math functions. I think on a digital scope MEAN(V1*V2) is going to give  the moving/instantaneous average of the instantaneous product of the two curves -- that is , the MA of the product of their two instantaneous values at time t.  As such, it's definitely not RMS.

[PhysicsProf]

We are using neither, but closer to the energy measurement you mention above.

We have been simply measuring input and output power using v(t) and i(t). It is the same result as the energy measurement, because the JT oscillation is periodic.

We've previously established the protocols for measurement, and all agreed that measuring the power is adequate and equivalent in this case. I hope you are not suggesting the contrary. It was also established long ago with Lawrence, that using RMS values is incorrect.

.99

 Correct.  We calculate the input and output power using the math function for v(t) and i(t) [from the voltage drop across a 1 ohm resistor, typically) and then take the MEAN value of P(t) = v(t) * i(t) over numerous cycles.  Not RMS values.

[feynman]

@PhysicsProf

I dug up my trifilar Joule Thief as well as my analog 2-channel tektronix scope.  So I can't give power measurements, but I will be able to photograph waveforms.   I'll post em as I get em.

I'm getting a digital 4 channel scope, but this will be a couple of weeks before I have this capability.

[PhysicsProf]

@PhysicsProf

I dug up my trifilar Joule Thief as well as my analog tektronix scope.  So I can't give power measurements, but I will be able to photograph waveforms.   I'll post em as I get em.

Looking forward to it, Feynman.  Suggest we start a new thread as this one is far from its starting point.

How does one set up a 'Bench'?  I like this feature here and would like to record thoughts and progress from my electronics bench...

[exnihiloest]

...
We have been simply measuring input and output power using v(t) and i(t). It is the same result as the energy measurement, because the JT oscillation is periodic.

We've previously established the protocols for measurement, and all agreed that measuring the power is adequate and equivalent in this case. I hope you are not suggesting the contrary. It was also established long ago with Lawrence, that using RMS values is incorrect.
...

Therefore I understand you calculate the power by summing (v(t)*i(t)) (not by making Vrms*Irms).
I perfectly agree, it is the right method. I was not suggesting any thing else. It was not clear for me what was used, and I just wanted to be sure (I don't master all subtetlies of English language), sorry if I disturbed the thread.
Thanks.

[poynt99]

Therefore I understand you calculate the power by summing (v(t)*i(t)) (not by making Vrms*Irms).
I perfectly agree, it is the right method. I was not suggesting any thing else. It was not clear for me what was used, and I just wanted to be sure (I don't master all subtetlies of English language), sorry if I disturbed the thread.
Thanks.

No problem at all exnih. Perhaps we are a bit touchy these days when anyone mentions using RMS for these measurements, as it seems we have to go to extraordinary lengths to change people's minds about the methods they were using. It required a lot of effort to make a little change, and I'd hate to have to go through all of that again.

Regards,
.99

[acmefixer]

Attached find a photo acquired at the University on 4 March 2011, the day the n = 1.13 value was obtained as explained in some detail above.  The photo was taken with my HP digital camera, which is not great for close-up shots, but by comparing with the schematic (also in the attached), I think you can pick out the essential elements.  For these tests, I used a power supply as described rather than a battery, and found that varying the input voltage was useful in changing the conditions of the experiment.  The best results were obtained at 0.996V input voltage.  Note that the power IN and power OUT are measured and compared, so the use of a power supply should not mitigate against the validity of the calculated N.

Hrm, some wires hanging loose -- another reason for a good closeup. One thing I can see, the black plastic transistor. A 2N2222 comes in a metal package, the PN2222A or MPS2222 come in the plastic package. One more unanswered question that needs to be answered before anyone can replicate the circuit.

Thank you for the followup.

[exnihiloest]

...
Anyway, with perseverance PhysicsProf should start seeing some numbers that refute his current findings suggesting over unity.
...

I admire your optimism.