how to make a stepper motor step gradually?

You could try just reducing the drive voltage to the stepper to reduce
torque. That may be enough, but it could en up being marginal (missing
steps with a heavy load). A superior solution is 'microstepping'. It
involves ramping the applied voltages to the windings using PWM and
can make for much smoother motion and greater positioning accuracy
(though there are practical limits on how much additional accuracy can
be gained).


Tim
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On Fri, 02 Jun 2006 13:34:50 +0100, Tim Auton


Depending on the setup, attacking the problem at another point might be
easier. For example, using a belt-driven system with the small pulley on
the stepper, large on the turntable, and a "soft" resilient belt.

--
Rich Webb   Norfolk, VA

more specifically i think you mean you want to reduce the current. in dc
motors the torque is proportional to current, speed is proportional to
voltage.

although by reducing voltage i suppose in effect, you are reducing the
current.

if you reduce the torque enough you should be able to slow the angular
acceleration down at each step.

Tim Auton wrote:

There is not an easy electronic solution to my knowledge, since you
rule out microstepping.You can consider mechanical solutions to damp it
a bit; for example, if you decouple the platform and motor, recouple
them through a helical spring, and add oil-damped vanes to the
platform, you might achieve the desired effect (at a loss of positional
accuracy).

Maybe reduce the voltage or current driving the stepper so it had less
power?  A simple resistor might work.

Or increase the mass of the platform so the power of the stepper would
create less of a jerk.

Gear down the motor so that each step created less of a jerk and change
your code to make it step more times.

Gear it down using a rubber drive belt to reduce the shock (like some of
the old record turntables?  Or use some type of soft coupling on the shaft
to reduce the shock?

Attach your object more firmly to the platform so it didn't slip?

That's about all I can think of.

--
Curt Welch                                            http://CurtWelch.Com/
curt@kcwc.com                                        http://NewsReader.Com/

Someone else mentioned a spring type of dampener.  I think another easy
solution would be to use a piece of rubber as the coupler.  Perhaps a
length of pencil eraser (the white kind, which seem to last much longer
before rotting).  The lenght of the rubber would control the softness
or stiffness.