From: Mario. <em...@gm...> - 2008-09-18 23:33:21
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You can only *properly* diagnose PWM signal with an oscilloscope or a digital analyser. The PWM ramp-up or ramp-down may be really short (0.5s) for the DMM to notice. On Fri, Sep 19, 2008 at 4:47 AM, Sebastian Kuzminsky <se...@hi...>wrote: > Eric H. Johnson wrote: > > The run-away problem seems to be licked, at least for relatively slow > speeds. I am, however, still getting following errors at higher velocities. > These start to occur at about 3IPS. The motors should max out at about 12 > IPS. Max step rate on the motors should be 20 RPS * 200 steps per revolution > * 16 micro-steps per step, or 64000 steps per second. At 3 IPS, it should be > about 16000 steps per second. > > Yay! Thanks for the debugging work, Eric! > > Is this with the latest stepgen.c that I posted earlier today? > > > > I have base period set to 25000 nsec, and servo period set to 200000 > nsec. > > > > I assume the following error results from position-fb getting too far > behind position-cmd, but I do not know what needs to be done to resolve this > problem. > > What are you doing in the base thread? It shouldnt be needed for this > setup, as I understand it. > > I'm not sure how to approach this following problem. Matt Shaver > reported a similar problem... I think Steve found a bug in Matt's > stepgen config, but I'm not sure if fixing that bug fixed his following > error. > > 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? > > 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? > > > > 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... > > > -- > Sebastian Kuzminsky > Theo: "Julian? I haven't seen you in twenty years. You look good. > The picture the police have of you doesn't do you justice." > Julian: "What do the police know about justice?" > > ------------------------------------------------------------------------- > 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...@li... > https://lists.sourceforge.net/lists/listinfo/emc-developers > |