[Open_electroporator] Culture Shock yardboard testing

[John Griessen]

On 06/24/2016 08:41 PM, John Griessen wrote:
> I had thought I would be able to "just use some test equipment" to make
> push and pull pulses to drive a push-pull converter rig up on the yardboard,

I've got one of the 4 transformers with 95 turns ratio rigged up for push-pull,
and I've driven the push side, (can't do push-pull without destroying until
pulses are commandable via micropython).  It shows transformer action with
some ramp up delay, and stops giving more output at around 1000V with
doubler + load out of the transformer.  30 k Ohms load is going to need bigger
wire in the transformers, and probably a little extra core material too is
my gut feel after reading more about transformer design.  The photos attached are
the best yet, but still not ready to use as is because of low output volts...

Looking at waveform yardboard-v0.3-0.jpg, yardboard-v0.3-1.jpg, yardboard-v0.3-2.jpg,
you can see a negative going pulse at the upper left getting wider and widest
in yardboard-v0.3-2.jpg.  From 0 to 1 the middle trace gets a teeny bit taller,
(see first division at left), but then in the next one no taller -- core has reached saturation.
The pulse getting wider is DC current flowing, (bottom trace).

Another thing you see in the negative going pulse at the upper left is it can't go
down to 1 Volt like it did up to 30 microseconds long -- there is too
much current required for the transistor to handle as it is set up with
resistance to the base.  The transformer is starting to look like some DC resistance,
which is much lower impedance than its usual reactive impedance.

If this was an ideal transformer, the middle trace would look just like the top trace,
but inverted and bigger, where we see it slews up in voltage and just starts to top out
like the input pulse does, when the core saturates and it's all over.

Next I'm working on micropython bring up and coding on the nucleo-F401RE
eval board from ST.
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