jeremy

Good afternoon all.

I have this bipolar stepper motor from sparkfun (https://www.sparkfun.com/products/9238) and I am driving it direct with a L293D. The full step is 1.8 degrees.

I'm using sine/cosine current ramps via PWM to implement the microsteps.  Using 8 microsteps the motor is really behaving as if it is half stepping.  The initial ramp up and final ramp down are not moving the shaft.

Since I have managed to microstep a 7.5 degree step motor with this technique I believe that the static friction is too high for the smaller microsteps to move the shaft.

This is discussed nicely in the Microchip Application note AN907.

So, has anyone else noticed that microstepping a small stepper can be very, very choppy?

Regards

J.