Hmmm - just noticed nobody replied to this. Sebastian Kuzminsky wrote:
>[snip] > >The wiki FollowingError page, ><http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Following_Error>, suggests >that following errors with steppers might be because ferror or >min_ferror are too low, or maxaccel or maxvel might be too high. (BTW, >that page has a broken picture on it.) > >How does emc2 decide that a following error is happening? > > When the motion function is run, the feedback position (synthesized in the case of stepgen) is compared to the command position, and a following error is signalled if the difference is above the allowable ferror (calculated based on speed). This is done before a new position is calculated. >Is it true that when emc2 interprets g-code, it makes a long array of >points (in whatever axis-space the machine operates) and feeds each set >of coordinates to the position-cmd pins on the controllers for the >various axes? > > No, not at all. The trajectory planner runs every servo period, and calculates the pose the machine should be in at the next servo period. This takes into account accel, decel, max vel, feed override, feedhold, etc. >>Secondly, now that I am back to it, the PWM does not seem to be changing. It >>is either off, or what seems to be close to full on. My meter reads either 0V >>or 3.16V. I did find that a mirror must have gotten bumped, resulting in >>apparently low output from the laser. Following a beam alignment, laser power >>does look to be close to full on. >> >>Any ideas on how to troubleshoot this is appreciated. >> >> > >I think measuring a PWM signal with a voltmeter isnt reliable; it >depends on how fast the meter is. Isn't there some simple RC circuit >that can be placed between the PWM pin and ground to make a >duty-cycle-controller voltage that can be reliably measured with a DMM? > I really dont know but I think I read something like that... > > Put a capacitor and resistor in parallel to ground. The time constant should be significantly longer (10x or more) than the PWM base frequency. Time constant = R*C, you get seconds with resistance in ohms and capacitance in farads, or microseconds if you use microfarads for C. - Steve ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
