Re: need help compiling EMC

[Jon Elson <elson-at-pico-systems.com>]

Hassan Rabe wrote:

> hello list.
> i have a problems with controlling a stepper motor...that delivers 0.25
> degree per pulse...when i calculated the required pulses per inch ...it was
> 11520..which i think a lot....but it worked out fine with EMC.....but my
> problem is that i can't get the feed rate to go over 9....and the axis speed
> to go over 10....the settings are in inches...

In the xxx.ini file, there are parameters for default_velocity and maximum_
velocity.  You set the maximum for the greatest speed the machine can
operate at, and the default is where the jog feed slider starts out at at
program startup.  These numbers are in user units (inches) per SECOND.
So, 2.0 means 1 IPS or 120 IPM.  Check the settings in your .ini file.
The second limit is the rate at which the computer can send pulses.
There is a period parameter (with freqmod.o) that sets the interrupt
rate.  Pulses can't be sent faster than every other cycle of this period.

10 IPM for you would be 11520 * 10 pulses per minute, or 115200,
which is 1920 pulses per second.  this would need an interrupt rate
of at least 3840 interrupts/second.  If you are using steppermod,
you might be able to run this fast, it depends on the CPU speed.
It would take a pretty fast Pentium to run this fast with freqmod.

Note that with either of these step output routines, when you get close to the
maximum rate, the jumps in step timing become so large that the
motor can't follow them.

> the motor is a 2 phase unipolar stepper motor...2A DC, ...i built the
> controller ..its mainly an EDE1200 microcontroller and a some transistors,

Oh, wait a minute.  I don't think this is an EMC problem.  Unipolar drives
are well known to generally perform poorly.  You are already getting
almost 2000 steps a second!  That is EXCELLENT for a unipolar drive!
You may be able to do better with a bipolar chopper drive, but you are
asking for a lot out of a stepper.  If you really need this level of
resolution,
you should look at 5-phase steppers or servo drives.

Jon