How to Choose a Stepper Motor

by Contributor

Stepper motors are being used more and more by hobbyist for projects from robotics to home-built CNC machines. Many of these projects revolve around the specialized functionality that stepper motors are designed for. Let's learn about the properties of stepper motors that should be taken in to consideration when selecting the proper motor for a task.

Determine the resolution needed. Stepper motors have a property called "step angle", this is the number of degrees the shaft turns per input signal from the control circuitry. Common step angles are 0.9 degrees, 1.8 degrees and 3.6 degrees. These step angles translate to 400, 200 and 100 steps per rotation. The greater the number of steps per rotation the greater the precision afforded by the motor. Some project may require a high degree of precision, as in the case of a CNC machine or robot.

Choose a winding scheme. Stepper motors can have their stator wound in either a bipolar or unipolar configuration. How the stator is wound determines the type of controller needed. In a unipolar configuration current flow had to be reversed to change direction, while a bipolar configuration does not, it provides two windings per pole, one for each direction. In general bipolar stepper motors allow for simpler control schemes for the hobbyist.

Determine the torque required for your application. Once you have determined the torque needed for your application, consult the documentation for a stepper motor and matching controller, and determine if it will provide sufficient holding torque.

Factor in the size, weight and power requirements when selecting a stepper motor. The physical design of some stepper motors is significantly lighter than other designs, this may be critical for a mobile application. Voltage and current draw may be dictated by the application and will factor in to motor selection. Remember the motor controller will be running at a higher voltage than the motor's rating.

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