On Mon, 14 Aug 2023, John Dammeyer wrote:
Date: Mon, 14 Aug 2023 16:36:16 -0700
From: John Dammeyer <jo...@autoartisans.com>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
To: "'Enhanced Machine Controller (EMC)'" <emc-users@lists.sourceforge.net>
Subject: Re: [Emc-users] Rigid tapping
Hi Andy,
I don't know. How can I tell? The encoder is connected to the MESA 7i92H
and according to my documentation is noisy so needs to be filtered. In
either case it looks like the MESA board is providing Velocity and Position.
I'd make a guess that based on its own internal clock it would provide a
usable velocity.
The problem, and might only be fixed in hardware is when I made the disk I
used a 4mm mill instead of the 3mm called for in the G-Code. Didn't notice
until the second slot at which point it was already too late. I'd guess at
this slow a speed that the encoder will provide two different speeds between
quadrature edges.
Must really fix that.
Here's some of the HAL file if that helps.
John
If you use LinuxCNC master, there is an interpolated position pin available
for hostmot2 encoders. This basically uses the velocity estimation and the
time since the last edge to get an estimated position between counts.
This should help the "staircase" motion of spindle synchronized moves
with low resolution encoders.
As far as noise goes and especially with low resolution encoders, this largely
reflects quadrature errors (deviations from 50 % duty cycle and deviations
from 90 degree phase shift between A and B).
Higher resolution encoders are better noise wise since since whatever
quadrature errors exist, the estimated velocity noise caused by these errors
gets divided by the counts per sample.
with low resolution encoders, you will typically have many samples between
edges so the best you can do is calculate the time between edges so even a
modest 10% duty cycle error causes relatively huge velocity noise.
Peter Wallace
Mesa Electronics
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