Stepper motor

A stepper motor is a motor that moves in steps as opposed to continuously rotating like other types of motors.

A stepper motor works by energising its electromagnets in a controlled sequence, meaning its output shaft turns in small, fixed steps. Giving precisse control of its position and speed

The key difference is how they control movement, stepper motors use steps and servo motors tend to use feedback to adjust speed and position

Torque, speed, operating conditions, position accuracy and load, these are the main things to consider.

No, an encoder is not needed on all stepper motors.

Stepper motors usually operate in an open-loop system: the control system sends a command to move a certain number of steps. Generally, there is no feedback to confirm the actual position. Servo motors, on the other hand, use a closed-loop system with a feedback device. The control system continuously monitors the actual position and speed of the motor and adjusts the current to correct any deviations, thus ensuring high accuracy.

Stepper motors provide good torque at low speeds but tend to lose torque as speed increases. Servo motors operate at higher speeds and maintain torque more effectively across a wider speed range. Stepper motors are often more cost-effective and offer predictable positioning, while servo motors are better suited to applications requiring rapid acceleration and changing loads

Servo motors offer better positioning accuracy because they use feedback from an encoder to monitor. Stepper motors move in defined steps, can provide good positioning accuracy without feedback, but struggles with higher loads. Depending on the application's load, speed and accuracy requirements will depend on the best option.

Servo motors typically maintain positioning accuracy better under changing loads and at higher speeds because they use encoder feedback to detect and correct positioning errors. Stepper motors can provide accurate positioning without feedback when correctly sized for the application. The best choice depends on the load, speed and accuracy required.

Stepper motors are usually a more cost-effective option compared to servo motors.

A stepper motor is the better choice for applications requiring precise, repeatable positioning and cost is a consideration. It is suitable for predictable loads, low to moderate speeds and systems that need good holding torque without complex feedback control.

Typically, servo motors are more energy efficient in applications with changing loads, frequent movement or high speeds. Stepper motors, when used in open loop, often draw current even when stationary to maintain holding torque, which can generate heat and use more energy. However, the most efficient option will depend factors such as the motor, controller, load and operating conditions.

There are several ways, depending on the motor and controller. You can change the direction setting in the control software or change the signal to the driver’s DIR input. For a typical bipolar stepper motor, you can also swap the two wires of one coil, with the power switched off. Alternatively, if the controller firmware directly controls the coils, you can reverse the stepping sequence.

A stepper motor’s available torque depends on its speed, current and driver settings. Typically, you would use the manufacturer’s holding torque specification when the motor is stationary and energised, and its torque–speed curve when it is running. There is no single simple formula that accurately calculates its torque under all operating conditions.

Stepper motors are controlled with a controller which translates signals into electrical current sequences into the stepper motor. This energizes the magnets within the motor and creates rotational movement in the form of steps.