[Open_electroporator] China transformers here to test

[John Griessen]

TL;DR:  It's a go.  These 5 samples are good for a first article.

I soldered one of the transformers to the yardboard, looked up my notes of how the program
was and how to load it, found out I didn't need to load a new one -- just use the last version,
brought up the power and oscilloscope, figured out triggering, and saw garbage on the screen.

I had one lead to the transformer still dangling.

Fixed that, saw traces that were familiar, worried they were too familiar, noticed that
one of the two transistors push and pull was not giving a big output, but the other was
shooting up to 1650 volts before the doubler.  Whew!  So, there is not a lot of margin,
and as I figure out tolerance design for the transformer and core materials varying I will
probably change the spec.  But the 5 first article transformers are all very closely matched,
so I can use them with their 3% tolerance to send to William, Alvaro, Nathan, and Keoni.

In the photo called "load = 33k Ohm + doubler caps", the voltage rises to about 1650 volts
in about 10 usec before hitting saturation.

In the photo called "load = 56k Ohm after xfmr", the voltage peaks about the same 1650V,
has an oscillating flat top at about 1300V, then hits saturation at about 5 usec instead of 10 usec.

having less load made saturation happen faster, which is a counterintuitive thing I
have come across studying magnetics -- current delivered to the secondary *REDUCES* total flux.

The sloping rise of voltage in "load = 33k Ohm + doubler caps" is because of the secondary winging resistance
in series with the capacitive load -- the doubler caps, diodes and 33o resistor.

When I code the timers to go fast without interrupts, I'll be able to do a 7 or 6 usec pulse
and not hit saturation by a big margin, so the first articles can use these transformers
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