What is a stepper motor?
A stepper motor is an electromechanical device that converts electrical pulses into distinct mechanical Physical motion. A stepper motor is widely used in various real-life applications, such as robotics, 3D printers, CNC machines, and automation systems. The working principle or pattern of a stepper motor involves the interaction between magnetic fields and electromagnetism to generate accurate rotational or linear motion.
A stepper motor is made up of three major components namely:
- A rotor also known as the shaft or the moving part.
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A stator that includes the coils and pole pieces.
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A control circuit that serves as the driver or controller that provides the electrical pulses to drive the motor.
The stator of a stepper motor basically consists of multiple sets of coils wound around single poles. The number of poles on the stator determines the step angle, which is the angular displacement of the motor per electrical pulse. Common step angles include 1.8 degrees (200 steps per revolution) and 0.9 degrees (400 steps per revolution) this simply implies that The step angle refers to the total number the motor rotates with each electrical pulse. It’s like a measurement of the distance the motor turns in response to a signal.
Different motors have different step angles. For example, if the motor has a step angle of 1.8 degrees, it means that for every single electrical pulse it receives, it will rotate 1.8 degrees. If you give it 200 electrical pulses, it will complete one full revolution which is 360 degrees. So, we say it has 200 steps per revolution.
When an electrical current is applied to an identified coil pair, a magnetic field is produced around the corresponding pole pieces of the stator. The arrangement of the coils and pole pieces determines the magnetic polarity pattern.
Stepper motors can have two common polarity configurations: which are bipolar and unipolar.
1. Bipolar :
In a bipolar stepper motor, each coil pair has two terminals, in which electric current can flow in both directions through the coils. By controlling the current direction and in a particular set of series of coils, the magnetic fields connect with the rotor to produce rotation. Then the driver circuit provides the necessary pulses to switch the current direction and control the motor’s motion.
2. Unipolar:
In a unipolar stepper motor, each coil is center-tapped, resulting in four terminals per coil. The center tap is connected to the same power source, and the other terminals are switched on and off serially. By powering the appropriate coil pairs in a particular series, the magnetic fields push or pull the rotor, thereby causing it to rotate. Unipolar stepper motors require additional driver circuitry to switch the current path through the coils.
The control circuit:
The control circuit or driver carries input signals, in the form of digital pulses, and converts them into the needed series of current flow through the coils. The driver circuit ensures that the electric current changes direction at the desired and needed timing to create the desired steps. It also controls the current levels to prevent overheating and protect the motor.
The step sequence function is to drive a stepper motor depending on the desired motion and the motor’s configuration. The two major step sequences are full-step and half-step modes. In full-step mode, abutting coils are powered together to produce a single step. while In half-step mode, the coils are powered to produce more steps, resulting in smaller angular increments.
By controlling the pulse frequency and sequence, stepper motors can achieve accurate positioning and control over their movements. The number of steps per revolution and the step resolution determine the motor’s precision. Higher step resolutions allow finer control but it definitely will require more complex control circuits.
Types of Stepper Motor:
In this informative and educative section, we will be taking a look at the various types of Stepper Motor available at the time this article was written.
1. Permanent Magnet Stepper Motor (PM Stepper Motor):
The Permanent Magnet Stepper Motor (PM Stepper Motor) is a type of stepper motor that uses a permanent magnet rotor. It comprises of a stator with multiple poles and a single rotor with permanent magnets. The stator windings are powered in series to create a rotating magnetic field that communicates with the permanent magnets on the rotor. This interaction causes the rotor to move in distinct steps.
The PM Stepper Motor functions on the principle of attracting and aligning the rotor’s permanent magnets with the stator poles.
PM Stepper Motors are widely used in various applications, which includes application in printers, scanners, and other consumer electronics.
2. Variable Reluctance Stepper Motor (VR Stepper Motor):
The Variable Reluctance Stepper Motor (VR Stepper Motor) operates on the principle of the different reluctance of the magnetic circuit. It comprises of a toothed rotor and a stator with multiple electromagnets. The rotor in the VR stepper motor has teeth that create a varying air gap between the rotor and stator as it rotates.
When the stator is powered in a particular series, the rotor connects itself with the electromagnet that offers the least reluctance path for the magnetic flux. The rotor moves Increasingly to reduce the air gap and optimize the magnetic flux link up.
VR Stepper Motors are mostly less complex in construction and provide good dynamic response characteristics.
VR Stepper Motors is used for head positioning in hard disk drives and floppy disk drives, ensuring accurate reading and writing of data tracks.
3. Hybrid Stepper Motor:
The Hybrid Stepper Motor combines both the features of the PM Stepper Motor and the VR Stepper Motor. It uses a rotor with permanent magnets and a stator with both permanent magnets and electromagnets. This construction allows for improved performance Output compared to the other two types of stepper motor.
The Hybrid Stepper Motors offer high torque, high holding torque, accurate positioning, and improved step resolution. They also provide smoother operation and better dynamic response than the other two Stepper motors, it is easy to say that the hybrid Stepper Motor is currently the best among other types of Stepper motors. Hybrid Stepper Motors are used in a wide range of applications, including 3D printers, CNC machines, robotics, and even in the medical field.
Real-life applications and uses of Stepper Motor:
In our day-to-day activities, we make use of a stepper motor without even knowing that we are, in this segment of this educative article we will give you a deep insight into where stepper motors are used and applied.
1. In robotic systems:
Stepper motors play an important aspect in robotic systems by providing accurate control over the movement of various components of a robot. These motors are used in the joints and actuators of robots, allowing them to move with accuracy and repeatability. The distinct steps of a stepper motor make it easy for controlling the position, speed, and torque of robotic limbs. Steppers control the number of steps taken and the direction of rotation, the robot can achieve precise movements demanded for tasks such as picking and placing objects in order, assembly operations, and even walking or crawling.
2. Applications in automobiles, assembly lines, and autonomous vehicles:
Stepper motors are widely used in industrial automobiles, particularly in assembly lines. They are used to control conveyor belts, robotic arms, and other moving parts, ensuring precise positioning and coordination of each task. Stepper motors are used in autonomous vehicles, enabling accurate control of The steering systems, throttle control, and braking mechanisms.
3. Stepper motors are used for 3D printing precise movement of print heads and build plates:
In 3D printing, stepper motors are important for precise movement control. They are commonly used to control the position of the print head and the build plate. The print head, which pushes the material layer by layer, depends on stepper motors to move accurately along the X, Y, and Z axes. The build plate, on the other hand, needs to be precisely positioned for each layer to adhere properly and for dimensional accuracy.
4. Stepper motors are used in computer numerical control systems(CNC Machines):
Stepper motors are used in CNC (Computer Numerical Control) machines, which are automated tools used for the purpose of precision machining processes. In CNC systems, stepper motors drive the motion of the cutting tools or workpieces. They receive digital commands from the CNC controller, which specific details on the desired position and movement. The stepper motors translate these commands into accurate rotational or linear movements, allowing the machine to accurately cut, and shape materials such as metal, wood, or plastic.
5. Stepper motors are used in Medical Devices:
Stepper motors are used in medical equipment and instruments for the purpose of controlling their precise accurate positioning capabilities. These motors are employed in devices that require controlled movement, such as surgical robots, diagnostic imaging systems, prosthetic limbs, infusion pumps, ventilators, etc.
For instance, in surgical robots, stepper motors play a vital role in providing accurate and controlled movements for robotic arms and surgical tools in surgical operations. Additionally, stepper motors are used in medical imaging systems like MRI machines and CT scanners to control the motion of the patient bed or gantry, prompting accurate positioning for scanning.
6. Used in Control and movement mechanisms of electronic Devices:
Stepper motors are used in different electronic gadgets to provide control and movement functionalities. They are found in devices such as electronic locks, which are used in safes or where access control systems are required, Digital clocks and timers are incorporated with stepper motors to drive the clock hands or display digits. The motors provide accurate movement and positioning of the clock hands, prompting accurate timekeeping and display.
In conclusion, stepper motors have a wide range of applications in both medical devices, automobiles, and end-user electronics. Their precise control, accurate positioning, and ability to perform predefined movements make them highly important in these different industries and more, I hope this article was able to give you a fundamental understanding of what a stepper motor is and what it is used for.
