Re: [TCML] Thumper, the worlds most advanced tesla coil.

[Michael Twieg <mdt24@xxxxxxxx>]

So I tried messing with the hysteresis network on my comparator, and I added
some extra shielding, but still got poor results, so I went ahead and
whipped up a variation of your predictor.  I think there are two things
desirable in a zero crossing detector:  a large dv/dt at the zero crossing,
and the appropriate amount of phase shift, which should be constant over
amplitude.  So I just made a LR shunt like yours, but used a large burden
resistor (10ohm) to give a large signal, then clamped it with diodes to
limit the signal to a range acceptable by my comparator.  Circuit schematic
attached.  I tried it out a bit and it worked intermittently; I think there
is another problem elsewhere to discover, but it's definitely a step
forward.

Also I'm starting to really dislike high speed comparators.  I'm using the
LT1711, which is 5ns, and it's too sensitive and interferes too much when it
transitions.  I'm thinking your AD790 might be a better compromise.

-Mike

On Wed, Jun 9, 2010 at 2:20 PM, Finn Hammer <f-h@xxxx> wrote:

> On Wed, 09 Jun 2010 14:20:20 +0200, Michael Twieg <mdt24@xxxxxxxx> wrote:
>
>
>
>> For your shielded electronics enclosure, did you connect the shield to
>> your
>> circuit's ground?  And did you tie all that to earth ground?
>>
>> -Mike
>>
>
> I never got around to implementing a grounding scheme. So everything that
> should be grounded is left floating.  =8-}
> My view was, that as long as all chips _in circuit_ were tied to ground
> with bypass caps, I'd be allright.
> I will, however, before the next run, tie shields, cooling fin and negative
> side of primary coil trough a 50nF bypass cap, to mains ground. Earth ground
> is usually too noisy to be of any use other than trying to keep the bottom
> of the secondary from jumping all over the place.
> It would be nice if you could supply pictures from your work.
>
>
> Cheers, Finn Hammer
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