Rosemary Ainslie Circuit Demonstration June 29, 2013 Video Segments

[TinselKoala]

@.99:

The only place that I can find the Figure 8, Paper 1 scopeshot is in the paper. She didn't post it to her blogs at the time, that I can find. But... she did post two shots taken just a few minutes later that are very interesting.

The Figure 8 shot was taken on 16 February 2011 at 9:26:01.
SCRN0183 was taken at 9:31:41
SCRN0184 was taken at 9:33:00

[poynt99]

Chances are that no settings were changed in that few minutes, but who knows. Fig.8 does appear different than the other two.

I don't see any current during the ON phase of the cycle. Is there enough +'ve gate drive?

[TinselKoala]

Well, it's hard to say what might have been changed. The paper doesn't give much information about the settings. But here's what I think.

The waveform seen in SCRN0183 and SCRN0184 look very much like the "turnips" that I get when using a triangle ramp, tilted over with the "symmetry" or duty cycle control to make a sawtooth with fast rise and slower decay, on the gate drive instead of a rectangular waveform. I think that the only difference between these two shots is the scope's horizontal timebase setting. The duty cycle and frequency of the circuit's waveforms hasn't changed.

The waveform in the Figure 8 scopeshot looks to me like it might have been made at a different frequency and duty cycle. I think I can see four "turnip" bursts per 500 microseconds (one per 125 microseconds)  with nearly no space between them, whereas the shots made a few minutes later are at 4 times that frequency and have about a 50 percent "on" or ramp positive duty cycle.
However it is possible that aliasing in the display could be masking the true shape of the turnips, and this shot too could be made with the same FG settings. It certainly does +not+ look like a shot made with a rectangle waveform on the gate.

As far as current flow goes.... I don't know. When I use the triangle ramp stimulation I get high heat in the load too. I think that the Q1 is turned on enough at the peaks to conduct significantly for a short time. These shots were taken during a time when she was reporting "stress" on the transistors, function generator problems etc. It is possible that she has selected the triangle ramp output of the FG without realizing it. For sure the FG in the PESN photos is set to make a triangle ramp.

Hmm.... Note that the Fig8 description gives the Period as "approximately 20 ms" and the Period of the later two shots read from the Gate drive signal is just about 20 microseconds.... and recall that she has made the "ms us" error before.

It's really too bad that we cannot trust any verbal descriptions from Ainslie at all. The only things we really _know_ are the data in the scopeshots and the photographs.

[poynt99]

TK,

Even the CSR scope traces are in question in my opinion. Zero current indicated can be easily accomplished by misplacing the probes as we've recently seen them do.

[poynt99]

TK,

I don't see any pattern at all in that Fig.8 scope shot. But without a description we can only speculate.