On Thu, 22 Jul 2021, Chris Albertson wrote:
Date: Thu, 22 Jul 2021 10:19:02 -0700
From: Chris Albertson
Reply-To: "Enhanced Machine Controller (EMC)"
To: "Enhanced Machine Controller (EMC)"
Subject: Re: [Emc-users] A new lathe encoder option.
Yes, time-stamping the
Yes, time-stamping the pulses works, if you have an accurate counter that
can be snap shotted by the pulse. A modern microcontroller or FPGA can do
that. But as the pulses get faster you have to transition back to counting
pulses not "ticks" or you have the same quantization noise problem.I
On Thu, 22 Jul 2021 at 04:01, Chris Albertson wrote:
>
> The noise here is not electrical noise on the cables. We assume the signal
> is perfect square waves.This is "quantization noise".
No, I am talking _specifically_ about electrical noise. With a single
pulse counter electrical noise
On Thursday 22 July 2021 01:02:26 dave engvall wrote:
> "The solution is to either add more counts per revolution or use a ten
> timesmore complex control algorithm."
>
> IIUC then the real problem here is statistical. That is the sample
> size is too small to be significant. Maybe an
t; > from thousands. Might be better to clean up the signals at the
> > source before they are ever counted.
> >
> > John
> >
> > > -Original Message-
> > > From: andy pugh [mailto:bodge...@gmail.com]
> > > Sent: July-21-21 11:54 AM
> >
"The solution is to either add more counts per revolution or use a ten
timesmore complex control algorithm."
IIUC then the real problem here is statistical. That is the sample size is too
small to be significant. Maybe an over-simplification of the issue but:
I think there are a couple of
"The solution is to either add more counts per revolution or use a ten
timesmore complex control algorithm."
IIUC then the real problem here is statistical. That is the sample size is too
small to be significant. Maybe an over-simplification of the issue but:
I think there are a couple of
ource before
> they are ever counted.
>
> John
>
>
> > -Original Message-
> > From: andy pugh [mailto:bodge...@gmail.com]
> > Sent: July-21-21 11:54 AM
> > To: Enhanced Machine Controller (EMC)
> > Subject: Re: [Emc-users] A new lathe encoder option
> From: andy pugh [mailto:bodge...@gmail.com]
> Counter-mode is a compromise for those short on pins. What this index
> mode offers is something better than the other current one-wire
> alternative which is A and Z on the same pin, where a spurious count
> puts you a whole turn out..
>
> --
> atp
On Wed, 21 Jul 2021 at 23:36, John Dammeyer wrote:
>
> It's been a while since I did quadrature programming but if you have two
> sensors don't the two work together to validate signals because they can only
> change under certain conditions. So noise can't totally screw things up.
Indeed,
at the source before they
are ever counted.
John
> -Original Message-
> From: andy pugh [mailto:bodge...@gmail.com]
> Sent: July-21-21 11:54 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] A new lathe encoder option.
>
> On Wed, 21 Jul 2021 at 1
On Wednesday 21 July 2021 17:19:05 Chris Albertson wrote:
> If you feed those averages to the PID controller, that PID is reacting
> to old data and you get either very sluggish control or oscillation.
>
> The best way is to predict the future and the have the control
> programmed to make that
If you feed those averages to the PID controller, that PID is reacting to
old data and you get either very sluggish control or oscillation.
The best way is to predict the future and the have the control programmed
to make that predicted future the future you want.That hockey
quote comes to
On Wednesday 21 July 2021 14:46:26 Chris Albertson wrote:
> Could you solve the noise issue with a phase-locked loop? THis takes
> advantage of the fact that the spindle has momentum and the
> accelerating forces are limited.
>
> It is a common technique in electronics, you build a good, clean
On Wed, 21 Jul 2021 at 19:49, Chris Albertson wrote:
> Could you solve the noise issue with a phase-locked loop?
Yes, this would be a far better solution. But I didn't want to
re-write the encoder counter from scratch.
Ideally you would use two PLLs, one for the pulses and one for the
index,
Could you solve the noise issue with a phase-locked loop? THis takes
advantage of the fact that the spindle has momentum and the accelerating
forces are limited.
It is a common technique in electronics, you build a good, clean local
oscillator and then take your frequency measurement from that,
> I went with a hollow shaft (40mm bore) encoder directly to the lathe spindle
Which is a far superior choice, but if you have the hardware to count
a 1024 slot encoder with full quadrature you are probably not the
target market for the single-wire mode of the software encoder.
--
atp
"A
I am guessing that these may therefore be an option too
http://trigger-wheels.com/store/contents/en-uk/d5.html
you can get custom ones / made to your measurements too
I went with a hollow shaft (40mm bore) encoder directly to the lathe spindle
one of these (or a variant of)
On Tue, 20 Jul 2021 at 23:40, John Dammeyer wrote:
> There is no reason a second sensor couldn't be added to provide quadrature?
It might work. I didn't test it.
It only detects the gap when counting up. But other than that the use
of quadrature is not specifically excluded.
Shall we say that
On Wed, 21 Jul 2021 at 05:36, andrew beck wrote:
>
> Andy what do you think is the max rpm that this will read reliably do you
> think?
It will handle a higher speed than a full quadrature setup as it only
needs to see one edge.
I have run it up to 16000 rpm (in the video) with a 50,000ns base
Andy what do you think is the max rpm that this will read reliably do you
think?
On Wed, Jul 21, 2021, 11:26 AM Andy Pugh wrote:
>
>
> > On 20 Jul 2021, at 23:40, John Dammeyer wrote:
> >
> >
> > Nicely done though. Is the code available for a look see?
>
>
>
> On 20 Jul 2021, at 23:40, John Dammeyer wrote:
>
>
> Nicely done though. Is the code available for a look see?
https://github.com/LinuxCNC/linuxcnc/commit/c73b402ad5a26a5509f8ba16915bb200fbe5d109
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Nice work!
On 7/20/2021 6:00 PM, andy pugh wrote:
I have added missing-tooth index to the software encoder (only in master).
https://youtu.be/t48TnJQtbCw
This opens up a number of large-bore encoder options, as this is the
scheme used on crankshaft trigger wheels.
options:
That's exciting because it does away with the need for a set of large diameter
toothed pulleys turning a quadrature encoder. One of the things that kept me
away with my larger bore South Bend Lathe.
There is no reason a second sensor couldn't be added to provide quadrature? As
long as the
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