yeah that would be easiest, but I want to do something similar for
azimuth and altitude.
On 7/13/20 9:00 PM, Dave Matthews wrote:
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
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