Hi Chris,
for the go to part I am not "too worried"about that possibly not being
too smooth, of course it is the goal to do that, but
the point there is to get there.
The equatorial tracking indeed needs to be as smooth as possible. With
the hearing I have I think I can run the stepper motors smooth
without having to do any micro stepping.
thanks,
Ron
On 7/14/20 3:49 AM, Chris Albertson wrote:
Gene is correct when he wrote the precision might be off when
micro-stepping.
Motors are mechanically built for 1.8 degree steps so that is likely to be
accurate but half steps depend on the driver.
But what I wanted to add is that when you read the speed vs. torque curve
it is for FULL steps. The amount of holding torque is reduced with
microsteps. It makes sense too, full steps use full current that is
switched between coils just 100% on or 100% off. With microsteps one
coild gets perhaps 3/8 of full current and the other gets something like
5/8. So the current is overall reduced.
In any case, run the motors at a step rate that causes them to run smoothly
without actually stepping. You want to see continuous motion.
BTW I'm using a DM542, the same driver you have on this vertical axis test
(link below). It has enough power even when doing 1/2 steps to move a 35
pound chunk of steel up and up at a decent rate of speed. machine is
obviously not balanced like a telescope The DM542 is set for only 2.0 amps
so it is not running at full power. SO you will be fine even with the
reduced torque.
This is the first time this axis ran. Just some jogs up and down. But
listen to the motor, you can't start and stop these stepper motors
instantly the velocity ramps up and down. In fact this rate of change is
as fast as I can go with this setup and the DM542's 2.0 amp current limit.
If you do a fast slew to a target, you need to ramp up the speed then
slow down and hit the mark and then pick up the star tracking rate. That
second loop controls the speed and the rate of change of that speed.
Software was to plan the motion in advance so that it start to slow soon
enough not to over shoot
https://youtu.be/tlMTksuOuZQ
On Mon, Jul 13, 2020 at 11:51 PM Gene Heskett <ghesk...@shentel.net> wrote:
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.
In theory yes, in practice, no. There is resistor tolerances and all
sorts of errors that can creep into a motor being held by the relative
balance of the currents thru 2 sets of coils.
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