On Saturday 29 December 2012 12:32:12 andy pugh did opine: > On 29 December 2012 10:11, Viesturs Lؤپcis <viesturs.la...@gmail.com> wrote: > > Using them for initial commutation would be ok, but using them > > permanently does not seem like a good idea, because that signal is not > > differential and that is plasma table, so I expect some noise in the > > signals, > > A momentary glitch in a Hall signal may well cause a momentary torque > glitch, but it should recover immediately upon the next valid signal. > As long as your positioning doesn't go wrong in that millisecond by > enough to matter, it should be OK.
Which is why, when I looked at his halscope traces of those sensor timings, I failed to see anything off far enough to do more than a rather minor irregularity in the cogging effect, a 10% wibble in the torque at worst. So I am inclined to do the un-thinkable, and hang some 10x scope probes on the drivers outputs. That will need a more than dual trace scope however since you need to see all 3 at the same time. And the eyeball training to recognize a voltage waveform from a bad driver for what it is. Even I, with 60 years of staring at scope traces, often have to stop and analyze the waveform I am seeing very carefully when I am looking at voltage & trying to imagine the currents flowing through a highly inductive load. In fact, now that I think about it, it would be ideally best not to analyze the voltages, but to sense the currents flowing thru a milliohm resistor. Since we're probably talking about an HBridge drive, which has no common ground point, best inspected with the full bandwidth of an un-amplified hall effect probe. 3 of those sparkfun BOB-08882's at 9.95 ea. made up into a test kit, might be the most educational $30 (USD) ever spent if a suitable scope to display their output is available. Obviously something deeper than the timing of the hall patterns is wrong there. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! Andrea: Unhappy the land that has no heroes. Galileo: No, unhappy the land that _____needs heroes. -- Bertolt Brecht, "Life of Galileo" I was taught to respect my elders, but its getting harder and harder to find any... ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. SALE $99.99 this month only -- learn more at: http://p.sf.net/sfu/learnmore_122912 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
