[Open_electroporator] China transformers here to test

William Beeson beesonwt at gmail.com
Sat Oct 1 16:24:25 UTC 2016


Thanks for the update!  Are we close to the point of testing these in an
electroporation experiment with E.coli/fungi?

On Fri, Sep 30, 2016 at 11:59 PM, John Griessen <john at cibolo.com> wrote:

> 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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