PhysicsProf Steven E. Jones circuit shows 8x overunity ?

[Magluvin]

in the middle of winding a trifi by hand, be back in a while. 
mags

[TinselKoala]

Even with the resistor inline, how can you compare brightness between an led that is driven with dc or a pulse/AC/on and off   on and off for periods of time?
Will the light meter being used average out when the led is lit and not lit during the pulse/AC cycle?

So I would say that if the pulsed/oscillated led is reading the same brightness, then I would also say that there is more energy sent through the pulsed led than the continuous dc led, to achieve the same brightness levels.

Mags

Take a solar cell (photovoltaic) and hook a resistor across it. Monitor the voltage output with an oscilloscope. Make a little light tight fixture that will contain the PV and your test LED. Do some DC calibrations.... easy enough, right? Put a known DC current through the LED and look at the voltage trace from the PV. Use several different DC currents, compute the associated power values, and plot your results on a graph: Power in to LED, Power out from PV. Now you have a DC calibration of your PV.
Now hook the same LED to your JT circuit or other oscillator. Monitor the PV with the scope.... instead of a straight line like in the DC calibration, you should see some peaks that correspond to the LED's brightness fluctuations. The area under these peaks will be proportional to the illumination's power, just as the area under the DC straight line is proportional to the DC power. You can compare the total light energy for a given DC current (read off your graph) with the total energy in the pulsed case by adding up the areas during a suitable time frame.
Then, if your LED is a known type, you can do an absolute calibration, because the light output at a given DC current should be on the data sheet.

I'd also recommend doing a "psychophysical" calibration: Use 2 identical LEDs, one to the JT oscillator at a known input power, and the other a DC variable voltage input. Sit in the dark, vary the voltage until the variable LED is the same apparent brightness as the JT LED. Measure the DC current. Change the JT input power, repeat the adjustment of the adjustable LED, plot the results, calibrate absolutely with the data sheet at a known current.

I think the diode, whether it's an LED or a regular diode, is needed for the proper functioning of an ordinary JT. I think.

[poynt99]

Great suggestion TK.

Mags, I wonder if you might take the time to address my above post? I know you're busy winding trifilars and all, but you haven't forgotten about us have you?

[Magluvin]

If it is implied that a diode or LED is still used ALONG WITH the "current resistor", then you are still using a diode or LED, correct?

If that is correct, then you are still using a diode or LED as part of the load, and just measuring the power in the "current resistor" is NOT going to give you an accurate measurement of Pout.

Now, if I am assuming incorrectly with the above, then please correct me. If not, then I am not twisting things, I'm simply trying to get clarity regarding the reference to "current resistor".

Well yes. But why not just say led as a load instead of diode or led?  To some, a diode is a diode and an led is an led.  What if a newbe goes out to rad shack to get some diodes to use as loads? or even someone that is just taking your word for it?
Specifics


"If that is correct, then you are still using a diode or LED as part of the load, and just measuring the power in the "current resistor" is NOT going to give you an accurate measurement of Pout."   

Well, the current through the resistor IS the current flowing through that branch of the circuit. The voltage across that resistor is V-Vdiode. So if we know Vdiode, it is simple math. 

Ah, you are right. Current resistor.  Ya know, I wasnt rereading it that way. Sorry. have a lot on my mind lately. Will try to be better prepared when replying.
lol I was looking back in this thread for the diagram you posted of where we discussed loosing the light bulbs for resistors. Couldnt find it and wen nuts, but that was Roses thread.   Right now, I dont remember the reason I had to use that example.  Couldnt get on here for the first half hour of my lunch here, due to the site only going to the home page. Im actually taking a longer lunch to respond here.

Hey TK

Can you produce a data sheet that shows output levels of an led throughout the power range? I looked for 10 min here at lunch and none so far show that.

I have to say that yes, if we have a map of the levels of brightness along side a power chart, then I would agree that we could measure power this way. And if there are no brightness/power charts, one could be made fairly easy.

All said, this would only work withing the safe limits of operation of the led used. Maybe if over driving it some, where the led is just not capable of producing more specified  wavelength output, but maybe more infrared(heat), then the sensor used would have to be able to read all wavelengths equally well. 

Is suppose it would be a worth while test to compare measuring the light output of the led and just measuring the "current limiting" resistor current x (V-Vled).

Hmm, it gets more complicated. If we only see the light output to measure power used from the source, does it figure in the "current limiting resistor" power used?  So we have to take note of both to know power used from the source.

Gota go. Im super late.

Mags

[poynt99]

Well yes. But why not just say led as a load instead of diode or led?  To some, a diode is a diode and an led is an led.  What if a newbe goes out to rad shack to get some diodes to use as loads? or even someone that is just taking your word for it?
Specifics

I thought I WAS being specific. When I say "diode or LED", that is precisely what I mean. In other words, one could have installed a diode OR a LED. Either would work, and BOTH have been used and discussed with JT replications. I was NOT implying that the two terms were synonymous!

Well, the current through the resistor IS the current flowing through that branch of the circuit. The voltage across that resistor is V-Vdiode. So if we know Vdiode, it is simple math.

You don't really believe it is that simple, do you? 

Consider the voltage "V" as you put it; what exactly does that wave form look like, and is the LED "ON" all the time? Is the current steady or fluctuating?

.99