Step Angle
The step angle is the angular displacement of a stepper motor's rotor in response to a single input pulse. It is determined by the number of phases in the control winding, the number of rotor teeth, and the energization mode. A smaller step angle generally results in smoother motor operation.
Common step angles include 0.72°, 0.9°, 1.2°, 1.8°, and 7.5°. Typical values by motor type are:
- Two-phase motors: 0.9° / 1.8°
- Three-phase motors: 1.2° / 1.5°
- Five-phase motors: 0.72°
Without a microstepping driver, users must select a motor with the appropriate number of phases to achieve the desired step angle. When a microstepping driver is used, the number of phases no longer determines the effective step angle — the user can simply adjust the microstep setting on the driver to change the motor's step resolution.
Microstepping
Microstepping divides each full step into smaller increments. Without microstepping, each pulse moves the rotor by the motor's full step angle. With microstepping, the angular displacement per pulse equals the full step angle divided by the microstep setting.
For example, a standard two-phase stepper motor has a full step angle of 1.8°. Without microstepping, one pulse produces a 1.8° displacement, requiring 200 pulses to complete one full revolution (360°).
Key Formulas
Pulses per revolution (with microstepping):
Pulses per revolution = (360° × microstep setting) / full step angle
Motor speed:
n = (60 × f) / p
Where:
- n = motor speed (rpm)
- f = input pulse frequency (Hz)
- p = pulses per revolution (microstep setting × pulses per revolution at full step)
Example: If the input pulse frequency is 1000 Hz and the driver's microstep setting is 2000 pulses per revolution, the motor speed is:
n = (60 × 1000) / 2000 = 30 rpm
Choosing the Right Microstep Setting
At higher speeds, a lower microstep setting is often sufficient, as high microstepping can reduce available torque at speed. At lower speeds, a higher microstep setting helps ensure smooth operation and reduces vibration and noise.