[Open_electroporator] Culture Shock transformer tests

[Nathan McCorkle]

John, for adding/overlapping pulses, was the idea to have a second
coil (and maybe third is required to get infinitely extendable HV?) ?

That seems like a test that could be done at lower voltage too, right
(overlapping/combining pulses to draw them out)?

-Nathan

On Thu, Jun 16, 2016 at 8:56 AM, John Griessen <john at industromatic.com> wrote:
> Wednesday I measured wire size of a likely transformer from a laser printer.
> That will help when deciding
> how to have a transformer made.  A laser printer power supply is about the
> right volt range when a doubler is used --6 or 7kV is why I am modeling mine
> after them.  The E shaped magnetic core halves used in them are 11mm on a
> side.
>
> Then I made a test circuit driven by  a lab pulse generator that could
> deliver 2 Volts to the primary side,
> and with a snubber diode as in the sketch visible with photo named
> transformer_test.jpg.  When I get more parts picked out that
> diode may go.  Running the test circuit showed a lower effective turns ratio
> than when open circuit.  The load was 30k Ohms on the secondary.  The
> ringing on the primary volts waveform may be partly instrumentation, but it
> can be reduced by a little capacitance at the 28 Volts stage.  More
> capacitance will be very likely since the input impedance equivalent for 30k
> ohm
> referred to primary "as if" there were no transformer is divided by (turns
> ratio)**2.  So the input impedance is about 10 Ohms reactive.  The DC
> resistance of the primary is 3 Ohms.  I sent some info to my most likely
> China supplier, but no response yet.
> They were the most responsive of several, but I may send some
> specs/questions to others soon also.
>
> Today, next, I build a transistor pulser with 28VDC.  Where will the little
> transformer saturate?
> We shall see.  Capacity of an E core to hold energy is related to volume of
> it for the same material.
> The maker of transformers says all range of core sizes are available.  About
> a ten microsecond pulse
> is OK for not making singing noises (frequency of the whole cycle can be
> above 30kHz).  I've not done this kind of test before, but I guess that as a
> pulse top goes out in time sagging at the secondary, the saturation limit
> will be reaches and
> the slight sag will turn into a cliff drop.
>
> John Griessen
> busy busy
>
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-- 
-Nathan