[Open_electroporator] Culture Shock yardboard testing

[Nathan McCorkle]

On Sun, Jun 26, 2016 at 6:12 AM, John Griessen <john at industromatic.com> wrote:
> On 06/25/2016 07:29 PM, Nathan McCorkle wrote:
>>
>> Hmm, aren't the diodes going to dump before you turn on the pull
>> transistor, making the transistor ineffective when you do finally
>> turn it on (assuming these are zener diodes)?
>
>
> They are just HV diodes in the doubler.  If you mean the ones next to the
> two transistors,
> no, they are just diodes also, and they are oriented opposed to the
> transistor turn on,
> so when the transistor conducts, they do not.  They are what is called
> freewheeling diodes
> that stop an inductive spike from taking out your transistors.

Right, I understand they are there to protect the transistors from
being over-voltaged... but isn't the point of the 'pull' transistor to
also take this spike and 'pull' it to ground? Or is this a 'pull' in
that the coil is wound oppositely, so it will actually cause a field
reversal?

When this is
> all sized right
> and not near saturation of transformer cores, a push pulse will always be
> followed by a pull pulse
> and the durations will be shorter.  The push and pulls need to be balanced
> to avoid too much DC and
> the resulting saturation.

Ok, so it seems the other coil is working to reverse the field... so I
guess the wire is wrapped in opposite direction (opposite rotation
about the core)?


Here are the specs on the small unit I used in school... seems to
assume the load is 3.3 kOhms, and gives a pulse for ~5msec
http://imgur.com/a/AJxwD

Am I reading it correctly that the pulse, though 5msec short in
duration, is providing 100 amps? Does that mean we need a power coil?
Or because we know we aren't using it with a constant duty-cycle
(should actually be relatively very low compared to normal power
applications), can we use a lesser transformer (I guess it will heat
up faster relative to a heftier coil)?


-- 
-Nathan