Testing the TK Tar Baby

[Rosemary Ainslie]

And guys

Just another red alert.  The shots that TK references do NOT show a 'high' current.  On the contrary.  His conclusions here are completely and utterly spurious together with his calculations.  I would earnestly caution you to simply ignore these posts of his.  They're hopelessly out.  I won't even bother posting those shots.  Even his comment regarding the LeCroy frequency is wrong.  This whole post an entire waste of time.  As usual.

Kindest regards,
Rosemary

SCRN0150.

This shot shows another high-current trial.... this time with only 48 volts nominal in the battery, so things stay under control. There is substantial DC power shown during the Gate HI signal, and even though the duty cycle is about 16 percent ON (not even including most of the ramp-up to steady state) the mosfet still will heat substantially at the 2.4 Amps it is carrying during that ON time.

Of course all this assumes that the same 0.25R current-viewing resistor stack was used for these trials. Who really knows.

So what magic happens during the oscillations, to prevent the NON oscillating DC current that happens at a DIFFERENT TIME from discharging the batteries? It must be magic indeed if the oscillations are NOT RECHARGING the batteries, as Ainslie acknowledges they are not, but rather are preventing the batteries from discharging  -- during a time when the oscillations aren't even present.

I will include a graphic showing my estimations from the traces for the DC portion of the period.

(ETA: I calculated the frequency based on my rough measurement using calipers against the blowup trace of 675 microseconds for the period and got 1481.481481481 Hz ( a repeating decimal, all digits included here for the Lulz only). Note the frequency given for the gate signal in the parameters box: 1.462 kHz. My eyeball measurement is different from the scope's computation by 19 Hz.... and 19/1462 is a little over ONE PERCENT. )

[mrsean2k]

"...This whole post an entire waste of time.  As usual."

I'll say.

But that's enough about your contribution.

Do you have information to divulge about the CVR? Did it have a different value rendering the calculation incorrect? Why do you dispute the frequency? It's a simple calculation from the information on the screenshot.

What specifically is incorrect?

[TinselKoala]

Ainslie: you idiot. I SHOW THE SHOT, you don't have to "bother to post" it BECAUSE IT'S THERE IN MY POST and I SHOW THE BLOWUP.

You don't think 2.4 amps is high current?

WHY DID YOU USE ONLY 48 VOLTS?

WHAT IS THE MEANING OF THE FREQUENCY SHOWN IN THE VERY BOTTOM OF THE SCREEN AFTER THE WORD "LECROY"?

@MrS2k:
She just makes stuff up out of her hallucinations. She probably cannot display images inline like the rest of us and is too blind to see the filename and look at HER OWN SCREENSHOT and HER OWN FREQUENCY DISPLAY of the blue trace shown on the scopeshot.
In other words she is a bloviating, lying idiot: she complains about something that she refuses to check, she makes false statements about it and insults people and tries to push her bogus agenda all at the same time: a willfully ignorant, lying, bloviating idiot, and that last post of hers proves it.

ETA: I'll allow that I may have overestimated the current. The voltage drop across the CVR may not be a full 0.6 volts but could be as low as 0.5 volts which would give a current of "only" 2 amps. This will still heat the mosfet Q1 substantially in part because, as GL has pointed out, its Rds is not going to be 2 Ohms in this linear amplification region but will be higher.  And of course since I am just considering the DC portion of the signal, the DC resistances are all that matter, no inductive effects come into the picture.

She has claimed "Upwards of 40 Watts" for this trial. Where does that figure come from? Does it come from the scope's numbers box? Is there anything on the screenshot that corresponds to the "40 Watts" figure? I see a -40.21 number there on the integration of the math trace values... but its units are
mVVs. Anybody like to try to decode that? I get milli Volt x Volt x seconds. Which is NOT "upwards of 40 Watts" so that Ainslie claim must be coming from somewhere else. Where?

ETA: Looking at the numbers in the parameters box for the "minimum" value of the math trace integral, and multiplying that first mV by 4 to convert to amperes we have -160 milliWattseconds.... an answer in Joules as it should be from integrating a power curve.... and if that is over the entire 5 milliseconds of the screen.....  we arrive at -0.160 Joules/0.005 seconds == -32 Watts, so we have indeed come close to the -40 Watt figure. Is this where it came from?

[TinselKoala]

By the way.... THIS is what an Integral of a (current x voltage) instantaneous power curve looks like, during the oscillations, making the NEGATIVE power product. Because, you see, the INTEGRAL of anything is a sum total, and if the bits that are "added" to a sum total over time are NEGATIVE.... then the value of that sum total MUST DECREASE over that time interval.

Like the RED trace in the scopeshot from Tar Baby below. The RED TRACE is performing the calculation INTEGRAL from t=0  to t= T of (CURRENT X VOLTAGE) dt, where the t=0 is the left end of the screen and t=T is whatever horizontal position you choose to look at for a vertical measurement of the trace. (Uncorrected for inductive reactance, which is only a scaling factor, it does not change the sign of the integral only the magnitude.)

Those numbers that the LeCroy shows in its parameters box when asked to compute the value of the integral of the displayed math trace... Can anyone tell me how those are to be interpreted? I know fully well how to interpret the actual INTEGRAL, as shown below, but that is not shown on the LeCroy, even though I think it could be.

[TinselKoala]

I thought that the value displayed in the numbers box for the "integral" of the CH1 CVR trace was not too informative.... but actually, now I realise that it IS informative, since I see it here in SCRN0150 displayed in a trial with substantial Q1 current.

Think about it. The value of the INTEGRAL of the CURRENT TRACE.... over the whole screen, I believe....  NEVER IS NEGATIVE, according to the scope's own calculations.

Of course.... the oscillation portion of the signal is undersampled..... so I don't really think that the scope's number boxes are correct for this type of mixed signal. The power in the oscillations and the DC power should be measured separately at different scope settings; the one used below is appropriate for the DC power level but not for the oscillations and certainly not for the mixed signal because the higher-frequency one is relatively undersampled. (Picket fence, Ainslie: you are looking at the oscillations through a picket fence with very large pickets and very small gaps. This is what is meant by undersampling.)