[sdiy] 4069 vco gives ground noise?

[Scott Gravenhorst]

René and I discovered that there is a sensitivity to which inverters
are used for what purposes.  I found two configurations that did not
work correctly.  When I hooked mine up like René's, it began to work
properly.  I didn't notice noise on ground, rather, I had a burst of
grass occuring on the PWM output when it should have been a single
solid edge.  René was able to reproduce what I saw by hooking it up
my "wrong" way.  Your problem might be related.

http://home1.gte.net/res0658s/fatman/VCO_pwm_tri_suboctave.html

See the center portion of the schematic with heavier lines.

This is a linear version of the same VCO showing the pinning that
works.  The one I built works very nicely.


=?iso-8859-1?q?Karl=20Ekdahl?= <_nial_ at yahoo.com> wrote:
>Hello everyone, i've built René Schmitz 4069 vco and
>stand alone it's working perfectly. But while adding a
>few modules to the same powersupply the ground line
>starts "wobbling". 
>
>Through my limited electronics knowledge i've
>recognized that if i put a 100k resistor inbetween
>ground and gnd pin on the 4069 i can reduce the noise
>but then the square out stops functioning. 
>
>Does anyone have any idea on why there's ground noise
>and how to prevent it?
>
>thanks
>
>/Karl
>
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