Lidmotor's Penny circuit help needed.

[Dark Alchemist]

What were the issues? Who were the people?

A real Joule Thief operates off a single 1.5-volt battery and has one or more LEDs as the load.  Because of it's somewhat unusual operating characteristics and the fact that LEDs complicate the output power measurement because they are what is called non-linear electrical devices it's actually much more complicated and difficult than you think.

The real way to do it would be with a digital storage oscilloscope.  Preferably you would have one with a built-in math function.  You have to measure the instantaneous voltage and current output by the battery, as well as measuring the instantaneous voltage and current across the LED.

It just happens to be a circuit where multimeters and a basic scope will not cut it and you can't really make the power measurement unless you have the right equipment and you really know what you are doing.

MileHigh

[TinselKoala]

Well, MH is right, but that's not a fatal issue! Don't let him scare you away from doing the analysis properly. It's not complicated, just tedious. Your MultiSim will surely do the required stuff as far as simulating the DSO's storage and math capability. And I've demonstrated several times how to do it all using analog scopes, screenshots and spreadsheets.

The current probe, once the scope is set properly, will give you the instantaneous current waveform through the measurement point, and you already have the voltage measurement in the other channel. I would be very surprised if the software could not multiply those together point-by-point and then integrate the resulting instantaneous power curve over the time of the measurement. Or you can ask the scope to give you the "average" value of the current, if that's all you are looking for. The peak current can be read directly from the traces once you have the scope set to display the signal properly.

[Dark Alchemist]

Well, I must be doing something wrong because as soon as I hook up a 1ohm resistor it will never start up.  I tried it in series from ground to the last LED's cathode and I tried it from ground to the anode of the first LED and no go with either.

[Dark Alchemist]

Here is a screen capture of a moment in time with my settings which are: X - 1us/div, Y - 1V/div ch1, Y - 2mV/div ch2 R2 - .1ohm

I am seeing negative current it seems but if my math is correct I am seeing 2.3mv/.1oh, = +/- 23ma or is my calculation faulty?

[TinselKoala]

Here is a screen capture of a moment in time with my settings which are: X - 1us/div, Y - 1V/div ch1, Y - 2mV/div ch2 R2 - .1ohm

Oh, have mercy! It's really hard to make out the scope screen from here, at the size/resolution you are posting. But I can see a couple of things. The blue Current signal isn't like any JT signal I've seen, it's more of a symmetrical sinusoid instead of the regular more-or-less rectangular pulses or spikes I generally see. But at least we can tell the frequency. You have just over 30 peaks in 8 microseconds.. .call it 30.1 cycles per 0.000008 sec, or around 3.76 MHz, which seems really high to me. And I can't see any corresponding peaks in the red Voltage trace, so I'm wondering if you've actually captured the true JT oscillation here or are seeing some other noise source.
When using a very small CurrentViewingResistor (CVR or CSR) it's easy to pick up noise. Since your system won't oscillate with a 1R in there (also a bit strange) I would try eliminating the resistor and the voltage-current conversion completely by using a pure "current probe" there if your sim allows it.

I am seeing negative current it seems but if my math is correct I am seeing 2.3mv/.1oh, = +/- 23ma or is my calculation faulty?

Well, as I said before I'm not sure if you are really seeing the current signal yet. But what I see on the Blue trace is 1 full division plus about 1/3 or 2/5 more, so that would be just under 3 mV (1 1/2 divisions would be 3 mV). And the same on the negative side. Your math is correct but you are reading the trace incorrectly, at least from my blurry view here.
However, your scope has cursors that you can position. The numbers and arrow buttons in the T1 T2 box "time Channel A Channel B" at the top left of the parameters area appear to be the cursor positioning and values section. So you can read the exact voltage peaks by using the cursors and reading the values you get here.

Also, at the bottom right of the screen are the scope's Trigger controls. Please set this at "Auto" or "Normal" and a level of about + 0.25 volts, ascending slope,  and use the Red channel, the Channel A, as you are using. What happens to the trace when you do this?

The JT I showed in the video above has a 1:1 transformer (actually 13 : 13 turns) and each winding has an inductance of 388-390 microHenry, measured on my ProsKit RCL meter and confirmed by my Arduino-based L meter. I can't tell what the coupling coefficient is but it's probably in the range you are using, 0.5-0.8, since it's a good ferrite.   It certainly doesn't oscillate at 3.7 MHz, though!

I might be able to modify this unit to "simulate" your simulation results in hardware by changing the cap values and etc. Let me see what I can arrange, and I'll give you some news later this afternoon.

But meanwhile, see if you can try the trigger setting I recommend, along with using the scope cursors to get precise voltage values from the traces. Also, if the 0.1 R CVR is causing noise pickup, eliminate it and use a "current" probe in the same position, if your sim allows.

I would apply the changes in this order: First, the current probe. See if your signal still looks the same. Then apply the trigger settings I suggest. The signal might disappear! If it does then try changing the timebase to 10 or 100 microseconds per division and see if the signal comes back stably on screen. If the signal doesn't disappear when you set the trigger as I have suggested but remains looking like it does now... then I'll have to play around with hardware myself to see what is up.

Bottom line: since I'm not seeing the characteristic JT-like peaks on the Red trace, and your Blue trace is so symmetrical and so high frequency, I am not confident that we are seeing the actual JT performance on the scope yet.

I've attached an example scopeshot from one of LTseung's JTs. Top trace corresponds to your Ch A probe point and bottom trace to your Ch B. The values you get will be different of course - especially the spikes/pulses should be narrower -- but the basic shape of the signals should be similar, I think. The symmetrical sinusoid of your Blue trace is atypical and I'll have to reproduce it in order to understand it fully.