ODP: thru zero VCO questions

[harry bissell]

Why not use a second set of comparators, outside the normal range, and
brute force the flip-flop via Set and Reset inputs, which dominate the
Data and Clock.

The pulse spray idea can be a 4093 gated schmitt oscillator.  The
comparator gates the oscillator, but after a delay the schmitt starts
firing pulses... The delay happens because the schmitt osc. cap has time
to rise to the positive rail... Following the gate it ramps down until the
threshold is reached, then oscillates from the +- threshold points...

See RCA (Harris) app note ICAN 6346 "Apps of the RCA-CD4093B COS/MOS
Schmitt Trigger" for details...
I didn't check polarities but you can use inverters etc...

By the way, what frequency range is useful for through-zero?? Is this an
LFO or 10Khz oscillator ????

:^)

Roman Sowa wrote:

> Maybe a second set of comparators (window comparator) with
> higher thresholds (by, say, 0.1V), so if the first set fails to toggle
> the FF and integrator goes beyond first threshold, the second set
> forces FF toggle. This only minimizes the risk of lockup. Not so good.
> BTW VCO is locked up until FM input changes polarity again.
>
> OR
> now I get Harry's idea of pulse spray. A clock oscillator (100Hz?)
> fed into AND gate, the other AND gate input goes to window comparator
> output. When integrator output exceedes valid range (copmarators
> thresholds) the AND gate issues next pulse. AND may be ORed with
> comparators output for normal operation.
> BUT
> If, after this second pulse from AND, the integrator couldn't make it
> below threshold, there comes another pulse making integrator
> change the direction. If FM input will be close to this 100Hz,
> and if appropriate phase relatioship occures, the integrator might
> go faster above thresholds than back to where it belongs.
> That's many IFs, but still...
>
> Roman
>
> -----Oryginalna wiadomooeæ-----
> Od: Rene Schmitz [mailto:uzs159 at uni-bonn.de]
> Wys³ano: 9 wrzeoenia 1999 16:54
> Do: Haible Juergen; synth-diy at mailhost.bpa.nl
> Temat: RE: thru zero VCO questions
>
> One has to use perhaps a mechanism to prevent the locking conditions.
> I hope to find the time soon to try it out.
>
> Bye
>  René
>
> error:asciiartisnotfully  \ uzs159 at uni-bonn.de
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>