It may just be my age but wouldn't it be easier to just use a 555 (do they still make them) and a knob to tweak the pulse rate to match the star? Add a slew button to change the speed while the button is pushed and a direction switch to toggle the direction pin on the driver. I guess I don't see the need for a computer to run a stepper at a constant speed.
Dave On Mon, Jul 13, 2020, 22:46 R C <cjv...@gmail.com> wrote: > well, I can calculate what the speed needs to be, also I can actually > "observe" it too.. by pointing the telescope at a star and see how > much the deviation is. I have encoder to check the actual speed of a > shaft. > > I found some information in a manual/tech-sheet that comes with the > drivers, so I am trying to figure out what the best stepping rate is and > what the best way of actually sending pulses to the stepper-driver is. > > I wrote some c-code that runs the motors in pthreads, I just want to > know what the best way is. pulse lengths, pause/gap length etc. > (basically the best way to use a dm542 (all those steppers are sorta > the same I understand) > > The driver tech-sheet basically says it can do pretty all it's > available micro stepping with a 1.8 degree stepper motor, I wonder if > that is really true. > > > Ron > > > On 7/13/20 8:35 PM, Chris Albertson wrote: > > A fast control loop that drives each motor at a given speed and a second > > slower control loop that figures out what that speed should be. The > > second loop typically uses "PID" even if only in fact the "P" is used. > > > > That can be used to drive any number of motors all at their correct > speeds. > > > > > > On Mon, Jul 13, 2020 at 7:28 PM R C <cjv...@gmail.com> wrote: > > > >> Interesting, > >> > >> > >> but I already have the motors, and the gears are on their way. What > >> I was really looking for is how to drive the stepper-drivers, he DM542 > >> series ones. > >> > >> > >> Ron > >> > >> > >> > >> On 7/13/20 7:53 PM, cogoman via Emc-users wrote: > >>> I recently discovered geared stepper motors. > >>> > >>> > >> > http://www.zyltech.com/nema-17-stepper-motor-geared-planetary-gearbox-1-7-a-3-1-nm-435-ozin/ > >>> > >>> I've been happy with zyltech in the past. I bought one of these for > >>> evluation, but the specs seem to be great for CNC. Low enough current > >>> to work with a stepstick, High enough torque for a fairly powerful > >>> machine, and less than 4 mH inductance should let it step pretty fast. > >>> > >>> 5.18:1 gear ratio should reduce that 4 meter spur gear, but the link > >>> below has higher gear ratios that would reduce that spur gear greatly! > >>> Backlash could be a problem for CNC, but if you are only going one > >>> way, the less precision gearboxes might be fine. > >>> > >>> > >> > https://www.omc-stepperonline.com/geared-stepper-motor/?sort=p.price&order=ASC > >>> > >>> Once you visit the stepperonline web page you know as much about them > >>> as I do, but their offerings might be just right for your application. > >>> > >>> On 7/9/20 2:23 PM, R C wrote: > >>>> Hello, > >>>> > >>>> this is (probably) off topic, been seen that happen. If it is please > >>>> ignore it. > >>>> > >>>> > >>>> I am building a "motorized" telescope mount (dobsonian) with what is > >>>> called an equatorial platform, it has 3 axis which I am going to > >>>> drive with stepper motors. > >>>> > >>>> > >>>> 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. > >>>> > >>>> > >>>> What I want to accomplish with the equatorial platform) (it > >>>> compensates for the rotation of the earth) is that, the start and > >>>> end position accuracy is not that important, smooth and > >>>> constant/consistent movement is. for the azimuth/altitude precision > >>>> is not a really big deal, but you'd want to move these 2 axis > >>>> somewhat swift. > >>>> > >>>> > >>>> So there are a few factors to decide. > >>>> > >>>> > >>>> I probably want micro stepping, what settings on the driver for > >>>> pulses per rev, is best to use (or is that just trial and error?) > >>>> > >>>> > >>>> As with PWM itself, I am probably just not too familiar with it. From > >>>> what I understand, the voltage I use for the motors determines how > >>>> fast I can go (I am going to use a 48V switching power supply). > >>>> > >>>> > >>>> as for PWM, I can of course change the length of the pulse itself > >>>> and, independently, change the time between two pulses. What is the > >>>> relation ship there? WHat does a longer width of the pulse itself > >>>> do? and what exactly does a longer gap between the pulses do (of > >>>> course the wider the gap between two pulses the slower the motor > turns). > >>>> > >>>> > >>>> for, especially, the equatorial platform, I want to avoid "jerking" > >>>> it, meaning starting and stopping the stepper motor as little as > >>>> possible and just go at a 'slow' constant speed. > >>>> > >>>> > >>>> > >>>> sorry if totally of topic.... > >>>> > >>>> > >>>> thanks, > >>>> > >>>> > >>>> Ron > >>>> > >>>> > >>>> > >>>> _______________________________________________ > >>>> Emc-users mailing list > >>>> Emc-users@lists.sourceforge.net > >>>> https://lists.sourceforge.net/lists/listinfo/emc-users > >>> > >>> > >>> _______________________________________________ > >>> Emc-users mailing list > >>> Emc-users@lists.sourceforge.net > >>> https://lists.sourceforge.net/lists/listinfo/emc-users > >> > >> _______________________________________________ > >> Emc-users mailing list > >> Emc-users@lists.sourceforge.net > >> https://lists.sourceforge.net/lists/listinfo/emc-users > >> > > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
