Re: Singing motors! :-)

> From: "Silicon Knight" <ttstam@...>
> Subject: Singing motors! :-)
>
> Hi,
>
> I am trying out EMC for Linux, and after a long battle finally
> got it compiled and running. sim.run runs okay, and the current
> motor setup runs fine under DOS with TurboCNC, but when I power it up
> under stepper.run in EMC, the motor makes a high pitch buzzing sound
> (before I issue any commands to move. Does anyone know what gives?

To possibles really. 1 - Deadband will affect either steppermod or
freqmod and should be set as suggested below. 2 - Tuning will only
affect freqmod but it can cause problems because I've seen some odd
values left in the tuning variables.

1 - I'd set deadband for each axis to a bit more than 1/2 of of one step
pulse. For examples, my Grizz uses 6000 pulses per inch or 0.0002 per
step pulse so I set deadband there for 0.00011. For the Sherline with
standard drive amp, it takes 16k pulses per inch (0.000062) so you'd want
to set deadband about 0.000035.

With low resolution setups, you'll see that the four decimal place
position numbers don't exactly match where you tell it to go because it
will stop and sit anywhere within the deadband range. You might tell it
to go to 1.0000 and what you see is 1.0001 or worse yet 0.9999. It is
only an aesthetic thing because the EMC is driving your motors to the
extent of their accuracy, but it can be annoying. To fix this you can
switch to commanded position rather than actual. If you would like to
use commanded as the default, you can edit the variable

; Initial display setting for position, COMMANDED or ACTUAL
POSITION_FEEDBACK = ACTUAL

then that setting will come up each time you start emc.

2 - The inclusion of stepper.run was intended to provide a general place
to start with stepper setups but some stray variable values got in there.
The tuning variables for each axis (I, D, FF0, FF1, FF2) should all be
set to zero. The P tuning variable should be set somewhere about 200 or
less.

> Also, does anyone have a Sherline / TAIG and don't mind posting
> their EMC.INI file? I am running Xylotex driver board,

It ain't no big thing, but you will find that with steppermod, the first
step after a direction change will be the wrong direction. Steppermod's
setup time and hold time for the relationship between step and direction
pulses is wrong for Jeff's hardware. The next time you reverse
direction it will switch back making the greatest error you'll see one
step pulse. Freqmod does not have this problem

> 116oz-in
> motor. I know that the INI file will need to be tweaked, but the
> more sample INI files I look at the better chance of me figuring
> something out.

All of the Sherline mods are available in the tarball on Sherline's site.
Contact me off list if you wish only that INI.

> The EMC Handbook's documentation is pretty
> arcane... :-(

Wanna help? These documents are in the repository and software to
download and edit it is available for most any operating system.

> Thanks!

Welcome. Thanks for the report.

Ray