Just like public relations officers, stepper motors know how to put just the right amount of spin on something. A stepper motor (also called a step motor or a stepping motor) is a type of electric motor that splits a full rotation into a discrete number of ‘steps.’ In other words, instead of turning an object continuously, it stops a certain number of times each rotation. Stepper motors are useful in motion control systems because they remove the need for feedback loops, which will be explained in further detail later in this article.

 

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Autonics’ 5-Phase Stepper Motor (Shaft Type)

 

Electric motors consist of two parts: a rotor and a stator. The rotor is the part that spins and consists of a bipolar magnet (which produces a permanent magnetic field). The stator is the part of an electric motor that stands still and is made up of multiple electromagnets (which produce temporary magnetic fields while they are turned on). What makes stepper motors different from traditional electric motor is that their rotor is shaped like a gear, or in other words it has multiple ‘teeth.’ Each ‘tooth’ is magnetic and contains an alternating pole – they are arranged north, south, north, south, and so on. This means that when the electromagnets in the stator are turned on and off sequentially, the rotor is pulled into perfect alignment, with its teeth lining up between the electromagnets in incremental steps.

 

Having a stepper motor in lieu of a traditional electric motor enables you to forgo having to install a position sensor. Ordinarily, when you are using an electric motor and you need it to operate with precision, you need a position sensor telling it to either spin more or spin less – for a variety of reasons, electric motors are notoriously inaccurate. This kind of setup is called a closed-loop system, because it relies on a feedback loop between the controller, the motor, and the position sensor to deliver the desired output response. Whereas a stepper motor can rotate an object by a desired amount of degrees, on command, without any external measurements needing to be made. A motion control system that includes a stepper motor is called an open-loop system.