In this article, we will cover the basics of stepper motors. You will learn about the working principles, construction, control methods, uses, and types of stepper motors, as well as its advantages and disadvantages.
A stepper motor is an electric motor whose main feature is that its shaft rotates by performing steps, that is, by moving by a fixed amount of degrees. This feature is obtained thanks to the internal structure of the motor, and allows to know the exact angular position of the shaft by simply counting how may steps have been performed, with no need for a sensor. This feature also makes it fit for a wide range of applications.
Stepper Motor Working Principles.
As all with electric motors, stepper motors have a stationary part (the stator) and a moving part (the rotor). On the stator, there are teeth on which coils are wired, while the rotor is either apermanent magnet or a variable reluctance iron core. We will dive deeper into the different rotor structures later.
In a normal brushed DC motor, voltage is applied to terminals which in turn causes a wire coil to rotate at speed inside a fixed magnet housing (the ‘stator’).
In this setup, the spinning wire coil (the ‘rotor’) effectively becomes an electromagnet, and turns rapidly at the centre of the motor based on the familiar principle of magnetic attraction and repulsion. A combination of brushes (electrical contacts) and a rotary electrical switch known as a commutator allows the direction of the current running to the wire coil to be alternated quickly. This creates continuous unidirectional spinning of the rotor coil for as long as the assembly is being fed with sufficient voltage.
A potential downside of this type of motor is that it spins continuously and for an arbitrary number of rotations until power is cut off.
This makes it very hard to control the exact stopping point of the motor, rendering it unsuitable for applications requiring greater precision control. Manually controlling the on/off flow of power to the motor can’t give you the required start-stop precision for performing minutely accurate movements.
In a stepper motor, the setup is quite different. Instead of a wire coil rotor spinning inside a fixed housing of magnets, stepper motors are built with a fixed wire housing (the stator in this case) arranged around a series of ‘toothed’ electromagnets spinning at the centre. The stepper motor converts a pulsing electrical current, controlled by a stepper motor driver, into precise one-step movements of this gear-like toothed component around a central shaft.
Each of these stepper motor pulses moves the rotor through one precise and fixed increment of a full turn.
As the current switches between the wire coils arranged in sequence around the outside of the motor, the rotary part can complete full or partial turns as required, or it can be made to stop very abruptly at any of the steps around its rotation.
Ultimately, the real strength of a stepper motor versus normal DC brushed motors is that they can quickly locate themselves to a known and repeatable position or interval, and then hold that position for as long as required. This makes them extremely useful in high-accuracy applications such as robotics and printing.
Types of stepper motors.
A bipolar stepper motor has an onboard driver that uses an H bridge circuit to reverse the current flow through the phases. By energising the phases while alternating the polarity, all the coils can be put to work turning the motor.
In practical terms, this means that the coil windings are better utilised in a bipolar than a standard unipolar stepper motor (which only uses 50% of the wire coils at any one time), making bipolar stepper motors more powerful and efficient to run. Although bipolar stepper motors are technically more complicated to drive, they tend to come with an inbuilt driver chip that handles the bulk of the necessary instructions and behaviours.
The trade-off is that they’re usually more expensive initially than standard unipolar versions, because unipolar stepper motors don’t require the current flow to be reversed in order to perform stepping functions - this makes their internal electronics much simpler and cheaper to produce.

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2. Hybrid stepper motor.
Hybrid stepper motors allow for yet more precision, through techniques such as half-stepping and microstepping. Microstepping is a way of increasing the fixed number of steps within a motor by programming a driver to send an alternating sine/cosine waveform to the coils. Doing this often means that stepper motors can be set up to run smoother and more accurately than in a standard setup.
Hybrid stepper motors usually have poles or teeth that are offset on two different cups around the outside of the magnet rotor. This also means steps and rotations can be more precisely controlled, as well as offering quieter operation, higher torque-to-size ratios and greater output speeds than standard stepper motors.
Applications of stepper motors.
Stepper motors have a wide range of applications in numerous industries and disciplines, with some of the more common uses being:
Computing, robotics, cameras, printing and scanning, including in 3D printers, process automation and packaging machinery, positioning of valve pilot stages for fluid control systems, precision positioning equipment
In this section, we’ll look a little more closely at some of these everyday applications.

1. Stepper motors for 3D printers.
Common 3D printer parts lists almost always include a stepper motor of some description. This is because the use of a stepper motor in a 3D printer is an highly accurate and cost-effective way of being able to perform very precise, accurate actions and rotations while the printer is attempting to translate information from digital scans into physical 3D objects.
Stepper motors and drivers in 3D printers allow for tightly controlled movement along both the X, Y and Z axis, either separately or concurrently, meaning that extreme accuracy of movement and positioning is achievable without the need for encoders and other additional software or sensors.
Most 3D printers will incorporate multiple stepper motors - they’re typically found in both the build platforms themselves and the filament extruders, where they’re used to help pull in filament and control the consistent, even supply of material to the machine throughout the full duration of a print run.
2. Stepper motors for CNC
Stepper motors are an alternative option to servo motors for powering most types of CNC machinery. CNC applications include a very wide range of manufacturing processes in which pre-programmed computer software controls the operation and physical movement of machine tools in factory and fabrication settings.
While stepper motors in CNC applications are often seen as a more ‘budget’ alternative to servo motors, this is an oversimplification based on knowledge of older technologies that isn’t always strictly accurate today. Stepper motors are indeed typically less expensive than servo motors for the same power, but modern versions tend to be just as versatile. As a result, stepper motors are far more commonly available, and found in a much wider range of machines and systems, from machine tools to desktop computers and automobiles.
CNC stepper motors also have one very key advantage over servo motors in that they don’t require an encoder. Servo motors are inherently more complex to understand and operate than stepper versions, and part of this complexity is the fact that they include an encoder, which is more prone to failure than most components in the otherwise reliable servo motor. Stepper motors don’t need an encoder, theoretically giving them even greater reliability than servos.
Furthermore, the fact that stepper motors are also brushless (unlike servo motors) means that they won’t require regularly scheduled replacement, provided their bearings remain in good working order.
3. Stepper motors for Raspberry Pi.
Stepper motors are an extremely common peripheral for adding to Raspberry Pi single-board computing modules for home enthusiast users teaching themselves the fundamentals of basic computer programming skills.
Raspberry Pi starter kits are usually sold in a very barebones configuration, with the idea being that the individual user will add whatever additional parts they like to their system in the order they choose to learn about them, adding to their skill set by learning to control new components using programming languages such as Python.
Among the Raspberry Pi user community, learning to manipulate and control small, inexpensive stepper motors is very commonly seen as a logical next step after learning to control LED on/off cycles and other simple switch or buzzer types. In effect, by linking a couple of these stepper motors in sequence, home hobbyists can begin to create a simple and programmable robot.
Many suitable types of stepper motors are available on the UK market for this type of application, starting from extremely inexpensive 5V versions that are easy to interface with headers on the Raspberry Pi motherboard.
4. Stepper motors for cameras
Stepper motors are widely used across a range of different applications in high-end camera technologies. They’re used both to control extreme precision internals, such as in-lens autofocus and aperture settings, as well as in the housings and external mechanics of security cameras and remote monitoring systems.
In particular, stepper motors and motorised camera sliders allow for very smooth operation of camera-positioning rigs, meaning that footage taken from security devices can be kept reliably free from potentially problematic image distortion caused by physical motion of the camera around its field of view.
Stepper motors provide several other attractive features for use in camera and video surveillance positioning systems, including full torque at standstill, extremely precise and immediate response times for all movement inputs, consistent repeatability of predetermined movements, and simple open-loop controls defined by fixed step sizes.
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Robotics