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

[Michael Twieg <mdt24@xxxxxxxx>]

I already have the allpass filter on the PCB and it works fine as far as I
can tell (by itself anyways).  I've also got a second order lowpass filter
on the current sense channel which was specifically implemented to reject
switching EMI.  My preference for the allpass is that it has a flat
frequency response, and is more easily tunable than an inductor.  My
suspicion is that having a number of active filters working on my current
signal is causing it to be more susceptible to stray capacitance (high speed
op amps don't like that stuff...).  Using the inductor for phase lead may
work because it doesn't  require active filtering, but I'll have to
experiment around to see.

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

On Wed, Jun 9, 2010 at 1:02 AM, Finn Hammer <f-h@xxxx> wrote:

> On Wed, 09 Jun 2010 02:28:25 +0200, Michael Twieg <mdt24@xxxxxxxx> wrote:
>
>  Thanks for the link, it was a really good read.  The mechanical design of
>> the tuning is incredible.  In a design I'm currently testing, I'm
>> implementing a phase lead using an all pass filter (can be tuned with a
>> potentiometer), so we should be able to get the same results as adding a
>> series inductor with the burden resistor.  However, I've had some issues
>> getting it working properly.  Our control scheme has two current
>> transformers on the primary, one of which is burdened with a resistor (for
>> measuring current) and the other is burdened with clamping diodes (only
>> for
>> zero-crossing detection).  When detecting the clamped-diode crossings, the
>> thing works fine, but when I try to have it trigger off of the burden
>> resistor waveform, it always starts oscillating at a very high frequency,
>> causing everything to freak out (not fatally, though).
>>
>
> I have never had the oscillations you mention, but I do bias the input to
> the comparator off zero by about 4-8mV. Not the same as hysteresis...
> I don't know much about allpass filters, but why not just have a go with
> the real thing, a simple inductor.?
>
>
> Cheers, Finn Hammer
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla