On 5/29/25 00:16, Peter Wallace wrote:
On Wed, 28 May 2025, John Dammeyer wrote:
Date: Wed, 28 May 2025 20:40:59 -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] Mill Spindle encoder with MESA interface.
Just an addendum. I do see that in the HAL file the motmod is
running with
1mS servo period.
loadrt [EMCMOT]EMCMOT servo_period_nsec=[EMCMOT]SERVO_PERIOD
num_joints=[KINS]JOINTS num_aio=8
So who or what is using the BASE PERIOD?
Normally with Mesa cards, a base period is not used, all real time
processes
run at the servo thread rate.
Low resolution encoders can work well for things like threading, as
you can use the interpolated position to get much higher than encoder
physical resolution, however interpolated position does not work as
well when there are reversals so for things like rigid tapping, a
higher resolution encoder is
better.
Slight correction feedback Peter, is "much much" better.
Depending on which gear my go704 is in, the scale with my setup is a bit
over 7000 in high gear, or something over 14,000 in low gear. And it can
run silently at 20 rpm or 3000. I have closed loop stepper/servos for
the axises that aren't and my next experiment will swap the motors and
drivers out, doing away with 3 PID's since the drivers incorporate their
own. I have 5 of those stepper/servo's in various places in the garage
now, they are stable and visibly more accurate than servo's or normal
steppers while running the motors both faster and 40C-65C cooler.
Savings seen in the monthly power bill.
-----Original Message-----
From: John Dammeyer [mailto:jo...@autoartisans.com]
Sent: May 28, 2025 8:30 PM
To: Enhanced Machine Controller (EMC)
Subject: [Emc-users] Mill Spindle encoder with MESA interface.
I've been asked how many lines an encoder on the spindle should have
for
LinuxCNC. I have a disk I made with 60 slots and IIRC someone else on
this
forum uses a gear tooth sensor. So a 400 or 600 line encoder isn't
really
required but likely there is a point where extra lines don't make any
difference.
Now with the MESA the encoder edges are counted in hardware so in
reality
likely the MOTMOD grabs the number every period and uses that for the
trajectory planning with respect to power tapping.
So here's the question. Are the encoder counts acquired from the MESA
hardware done on the BASE PERIOD or SERVO PERIOD?
Normally you wouldn't be power tapping at 3000 RPM so at slower speeds
higher resolution might be useful but at which point is there a
tradeoff?
Thanks
John
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Peter Wallace
Mesa Electronics
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Cheers, Gene Heskett, CET.
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