Hi, I'm *guessing* that they are the older Geckos (non digital). The older drives had to have the DIR line stable for quite a time after the STEP pulse. I believe this was to manage the resonance compensation circuit. This makes me think the DIR line was not actually latched at the time of the STEP pulse. If this is the case, the external DIR line would play an active role in the direction the current is going to be going in the motor windings. Thus, at the start of each PWM cycle (about 20KHz) the DIR line would determine which direction the current should go (even in a stationary motor). As the DIR line changes, the standby current in the motor will be reversed. The rate of DIR reversal coupled with the 20KHz ends up giving a beat frequency in the audible range. Another guess would be that the actual noise "signature" would be where the drive stopped within the 10 microstep range. You could end up having 10 different crackling noise characteristics depending on which microstep you stopped at.
While the noise might be annoying, I don't think (another guess) it would cause a problem for the drive as long as the correct DIR polarity is stable before the next STEP pulse comes in. Jeff ---------------------------------------- > Date: Sat, 22 Feb 2014 11:30:59 -0800 > From: p...@mesanet.com > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] Crackling motors using Beaglebone > > On Sat, 22 Feb 2014, Mark Tucker wrote: > >> Date: Sat, 22 Feb 2014 19:20:57 +0000 >> From: Mark Tucker <m...@rmtucker.f2s.com> >> Reply-To: "Enhanced Machine Controller (EMC)" >> <emc-users@lists.sourceforge.net> >> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> >> Subject: Re: [Emc-users] Crackling motors using Beaglebone >> >> John >> >> Thank you so much for the insight of how that work and it explains a lot. >> But as you stated it would be hunting back and forth.Which i assume it >> would have to pulse the step line? >> And a number of people have scoped the outputs and only found the Dir >> line hunting back and forth,i wonder why it is not detected on the step >> line.? >> And if it is only the dir line,why would the motors make a noise at all? > > > The internal stepgen position has a resolution of a small fraction of a step > (1/10000 of a step in Johns example) so it can hunt back and forth without > emitting a step. > > As to why a step drive pays any attention to the dir signal without a step > pulse I do not know, seems like a mistake to me. > > > Peter Wallace > Mesa Electronics > > ------------------------------------------------------------------------------ > Managing the Performance of Cloud-Based Applications > Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. > Read the Whitepaper. > http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Flow-based real-time traffic analytics software. Cisco certified tool. Monitor traffic, SLAs, QoS, Medianet, WAAS etc. with NetFlow Analyzer Customize your own dashboards, set traffic alerts and generate reports. Network behavioral analysis & security monitoring. All-in-one tool. http://pubads.g.doubleclick.net/gampad/clk?id=126839071&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
