Hi Ralph, I forget who said it, but... "It is not sufficient that there be no obvious bugs. It should be obvious that there are no bugs." (Probably Hoare or Dikstra or some other pioneer.) I believe your solution fails that test.
I could easily imagine a small amount of servo hunting in normal operation. That might happen just at the transition between encoders and have an extra count in one direction, but not the other. That might cause a gradual zero drift. I understand that you are "...not very worried about a couple of counts every 75mm." It would be nice to have a cleaner solution. On the other hand, "There are things worth doing that aren't worth doing right." This might be one of them. (Particularly since I haven't seen a "right" solution.) Regards, Ken On 7/12/2012 2:03 PM, Ralph Stirling wrote: > I solved my multiple-encoder problem for my linear motor. It turned > out to be almost trivial. The encoder counter doesn't care where it > is getting A and B signals from, just so each pulse represents a fixed > amount of movement of the carriage. So I connect all my A&B outputs > together with tri-state buffers and enable each pair in succession as > the "valid" signal of a new encoder becomes active. I can now make > my motor indefinitely long, with as many encoder modules as I want, at > essentially arbitrary spacing (no calibration needed), and no special > hal modules. Hal just thinks it is an ordinary brushless motor setup > with a single encoder. My logic (as currently implemented) consists > of two TTL logic chips per encoder head. > > It is possible to have a tiny glitch at the transitions, but since these > AS5311 encoder sensors have 2um resolution per count, I'm not very > worried about a couple of counts every 75mm. > > -- Ralph > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
