On Thu, 22 Dec 2011 17:13:11 +0000 andy pugh <bodge...@gmail.com> wrote:
> On 22 December 2011 16:45, Anders Wallin > <anders.e.e.wal...@gmail.com> wrote: > > > a dream project of mine would be a telescope mount. To minimize > > tracking error one should measure the rotation directly on the > > geared axis (not the motor) and one wants maybe 4 million pulses > > (22 bits) per rev for that. > > That sounds like a job for a resolver, rather than an incremental > encoder. I am not sure which chip the Pico converter uses, but the > same family go up to a claimed resolution of 2 arc minutes. > http://uk.rs-online.com/web/p/synchro-resolver-to-digital-converter/7094709/ > Not inexpensive, though. > Couple that with a multipole resolver and you might get what you want. > > > want an encoder with 12 to 14 bits of sine-shaped counts, i.e. up to > > 16k-counts/rev. How big a circle would that require? > > That depends mainly on the sensor. The sensor I am intending to use is > 75 lines per inch, so 16k would be a 68 inch circle.. > There is a 150 lpi version, for a mere 3-foot encoder. The fancy encoder on some Fanuc motors comes to mind. I think Jon Elson doped out how to read one of them. Dave > ------------------------------------------------------------------------------ Write once. Port to many. Get the SDK and tools to simplify cross-platform app development. Create new or port existing apps to sell to consumers worldwide. Explore the Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join http://p.sf.net/sfu/intel-appdev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
