On Thu, Jul 9, 2020 at 12:47 PM andy pugh <bodge...@gmail.com> wrote:
> On Thu, 9 Jul 2020 at 19:26, R C <cjv...@gmail.com> wrote: > > > The stepper motors I use with a stepper driver, those common DM542 ones, > > the stepper motors themselves are 2A and 1.8 degrees per step. > ... > > As with PWM itself, I am probably just not too familiar with it. > > Do you mean PWM? > > Stepper drivers take step and direction, not PWM. > > I think this is a job for an Arduino, rather than LinuxCNC. > Especially as I assume that an equatorial mount runs at an absolutely > constant rate anywhere in the world? > Almost, 1) the atmosphere refracts light more near the horizon than at zenith and 2) most telescope mounts flex as they move and 3) every worm and wheel system has at least some periodic error I worked on an astrometry (yes the spelling is correct) project where the units are "mas" or "milliarcseconds" At that level nothing is straight, square or constant. Today even amateurs on a personal budget can work at this level and it does matter if doing photography of planets. I'd recommend a microcontroller that has built-in floating point and it REALLY helps if it can run NTP off a GPS receiver so you get at least millisecond level time. Arduinos are not up to this unless they are connected to a PC So the design depends of if you want ot be dependent on a computer. Most users will have a PC or even a couple of them if doing photography That said, for casual visual use, a constant pusle generator is all you need, even the Arduino is overkill. You could use a 555 chip. But this person said THREE motors. So I think maybe it is an az, el system with field de-rotation. None of those rates would be constant. > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
