Re: Skipping steps, avoiding resonance

Hello all,

This is my first post and as a newcomer to this 'sport', I have
learned much here already just reading. I feel that lurkers are
probably welcomed but should make themselves known.

The degradation of signal and cross talk between digital as well
as converted ditital to analog information has been a current study
of mine. The analog servo system incorporated in the autonomous (800
lb.) helicopters that we are building is the case in point. Seven
channels were talking (jittering) when only one signal was present
to a single analog channel. I found that the unshielded signal
wiring and common grounding system were to blame, and shielding was
the primary culprit. We found that the conversion from digital to
analog was full of spikes that varied with load to one channel and
would cross-talk into an ajacent conductor and cause the driver to
go nuts. Filtering was tried but separate grounds and shielding
alleviated the problem to an extent. But, any conversion such as PWM
can be a problem with even leaky power supply capacitors, the
rectifiers can be a source of terrific spikes too - one badly
leaking one in a bridge... Diodes are noisey anyhow. Use a scope to
watch various areas of your signal paths - it's amazing what you'll
see.

Hoping this is not considered off topic, it may help correcting
some of the stepper and servo motor problems mentioned here. But I'm
no expert on the subject!

Thanks,

Bill C.