gEDA-user: challenge board ALMOST works

[Berni Joss]

On Sun, Sep 10, 2006 at 10:49:09PM -0700, Samuel A. Falvo II wrote:
> On 9/10/06, DJ Delorie <dj at delorie.com> wrote:
> >However, the two oscillators tend to self-synchronize.  If I let it
> >run, one LED is on and the other is off.  If I put scope probes on the
> >buffered outputs (pins 6 and 8), I can see that the oscillators are
> >running, they're just in lock-step.  Not even out of phase.
> 
> I think you accidentally re-discovered the "synchronous oscillator."
> Since all your inverters are on the same physical chip, the output of
> one is likely influencing the other just enough to result in
> synchrony.
> 
> >Ideas?  The only thing I can think of is inductive or capacitive
> >coupling, but at 400 Hz?
> 
> Even at such low frequencies, sharp transitions cause differential
> spikes to appear on adjacent wires, and it's possible that those
> perturbations can still cause circuits to interact.

You may also want to verify for coupling via the power supply ...

> 
> Ahh ... the life of an analog circuit designer.  :D
> 
> -- 
> Samuel A. Falvo II
> 
> 
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