Can I position accurately without an encoder?

Often yes for light loads and moderate speeds if the motor is sized with margin. Under heavy inertia or resonance, steps can be skipped; closed-loop steppers or servos add feedback to recover.

What causes mid-range resonance?

Spring-like magnetic stiffness and mechanical inertia create a vibrational mode. Driving near that natural frequency can amplify oscillation and stall the rotor. Damping, acceleration profiles, and mechanical design mitigate it.

Is microstepping always more accurate?

It reduces vibration and increases apparent resolution, but magnetic nonlinearities mean microsteps are not perfectly uniform without calibration and a capable driver.

How does this differ from the DC motor page?

DC motors are usually analyzed with continuous voltage, back-EMF, and torque constants. Steppers are discrete-field machines: the learning focus is sequencing, detent alignment, and pulse timing rather than a smooth torque-speed line.

Stepper motor (4-phase)

Full-step vs half-step commutation; rotor snaps as coils A–B–A′–B′ sequence.

About this model

A stepper motor advances its shaft in discrete angular increments (steps) when its windings are energized in a timed sequence. Unlike a brushed DC motor spinning freely under voltage, the stepper is designed for open-loop position control: each pulse ideally corresponds to a fixed rotation of a few degrees or less, depending on mechanical step angle and microstepping. Torque versus speed curves, holding torque when coils are powered, and detents when unpowered arise from the interaction of permanent or induced rotor flux with stator poles. This simulator foregrounds the *switching pattern*—full-step vs half-step vs microstepped sine-cosine currents—and the resulting rotor alignment, while simplifying magnetic saturation, eddy currents, resonance mid-band, and driver electronics. Students learn why sequencing matters, why missed steps accumulate if load torque exceeds pull-out torque, and how microstepping trades smoothness for complexity.

Who it's for: Robotics and mechatronics students comparing DC servos, steppers, and encoders for positioning tasks.

Key terms

Stepper motor
Stator
Rotor
Full step
Half step
Microstepping
Holding torque
Pulse sequence

How it works

Electronic commutation: energize stator coils A–B–A′–B′ in sequence so the permanent-magnet or variable-reluctance rotor snaps to the next equilibrium. Half-stepping energizes two adjacent windings to stop between full-step positions.

Frequently asked questions

Can I position accurately without an encoder?: Often yes for light loads and moderate speeds if the motor is sized with margin. Under heavy inertia or resonance, steps can be skipped; closed-loop steppers or servos add feedback to recover.
What causes mid-range resonance?: Spring-like magnetic stiffness and mechanical inertia create a vibrational mode. Driving near that natural frequency can amplify oscillation and stall the rotor. Damping, acceleration profiles, and mechanical design mitigate it.
Is microstepping always more accurate?: It reduces vibration and increases apparent resolution, but magnetic nonlinearities mean microsteps are not perfectly uniform without calibration and a capable driver.
How does this differ from the DC motor page?: DC motors are usually analyzed with continuous voltage, back-EMF, and torque constants. Steppers are discrete-field machines: the learning focus is sequencing, detent alignment, and pulse timing rather than a smooth torque-speed line.