Stepper motors: what it is, where it is used, device and principle of operation, types and their design features, stepper motor driver, connection and control - ElektrikExpert.ru

A stepper motor (SM) is a brushless mechanism with several windings and sequential voltage supply to each of them. The first instances of electric motors of this type appeared in the 1830s, and for almost 200 years the device has undergone significant changes.

Below we consider what kind of unit it is, what types and design features are, on what principle they work, and where they are applied. We will separately analyze the pros and cons, the intricacies of connection and control, as well as other issues related to the type of motor.

What is a stepper motor

A stepper motor is an electric motor, where a pulsed current supply leads to the movement of the rotor part at a given angle. Belongs to the class of brushless DC electric motors.

After starting it, the greatest torque is created at minimum speed, and the engine itself shows excellent performance even at rest.

The control is carried out by means of discrete pulses generated on the motor driver.

The first stepper motors had the form of an electromagnet that rotated a ratchet wheel at the moment of switching on. Each inclusion resulted in moving one position.

During operation, the motors have been significantly optimized in terms of design and functional parameters.

Scope

Stepper motors are widely used and are installed in many mechanisms.

examples:

Peripheral devices of computers.
Machine tools with numerical control (CNC): XY-tables, milling machines, drawing machines.
Computer memory devices.
Equipment for reading optical discs.
puncher and tape reader, etc.

CNC milling machine

Two-phase stepper electric motors of hybrid type have received active use in mechanical engineering. They are also used in the drives of various machines and mechanisms that operate in the “start-stop” mode.

Types and design features

Today, several types of step motors are used, differing in design, type of windings, control features and other parameters. Let’s consider each classification in more detail.

According to the design of the rotor

Many characteristics of the engine, regarding the speed of rotation and the mode of operation, depend on the rotor.

From this position, three types of device stand out.

Reactive (synchronous). Feature – the absence of a rotor magnet. Structurally made of special alloys to reduce inductive losses. The device has the form of a gear with teeth, and voltage is supplied to the stator poles from the second pair. As a result, a magnetic force is generated to move the rotor. According to the principle of operation, a reactive stepping unit has much in common with a synchronous motor, where the rotor and stator fields rotate in the same direction.

Motor with magnets. Unlike the previous device, the moving element is equipped with a permanent magnet with two or more poles. The rotor rotates due to the attraction and repulsion of the poles with the help of an electric field at the moment the potential difference is applied to certain windings.
Mixed. Hybrid devices combine the best qualities of magnetic and jet motors. Unlike previous models, the angle and step are smaller here. Structurally, the rotor is equipped with a permanent magnet having a cylindrical shape. Outwardly, it has the form of two poles with a circular cross section, on the surface of which there are rotor teeth. This feature guarantees good torque and holding. The main advantages are maximum smoothness, accuracy and speed of movement.

By type of windings

The smoothness of the operation of a stepper motor is directly dependent on the number of windings, so it is important to pay special attention to this factor.

Many mistakenly believe that the number of windings depends on the number of phases. This is not so, because even a 2-phase motor can have four or more windings.

Stepper motors are:

Unipolar. A special feature is the presence of a tap from the midpoint, which makes it easy to change the poles. The downside is the use of part of the turns, so the torque decreases. To increase the power, the middle output is not recommended to be connected. Structurally, unipolar devices contain five and six leads.
Bipolar. This group includes a stepper motor connected to the controller through four taps. The windings can be combined in parallel or in series. To change the direction of the current, so-called chips are used that provide manual control. Achieving this effect is available using the H-bridge. Compared to the unipolar type, the bipolar type guarantees the same torque but in a smaller size.

By type of management

To expand the functionality and ease of use, a control system is provided.

It is of the following types.

Wave: excitation of only one winding. The disadvantage is the minimum available moment.

Full step: simultaneous switching on of the windings.

Half stepping: cutting the geometry of a stepper motor in half. Provides increased resolution when positioning the shaft of the unit.

Type

When choosing stepper motors, you need to understand that they come in several types.

Let’s take a quick look at their features:

Bipolar motors are two-phase with an angular displacement of 0,9 or 1,8 degrees. The developers guarantee high step accuracy without load up to 5%.
With encoder (often called hybrid servomotors). The peculiarity is the presence of an incremental encoder. Motors combine the best qualities of servo and stepper electric motors, and the price of such devices is less compared to a servo system. Used in conjunction with a controller.
Linear (actuators). The principle of operation is based on the transformation of rotational motion into linear. In other words, they combine a screw gear and a stepper motor, combined in a common unit.
Stepper motors with gearbox. They are used in situations where it is necessary to obtain the maximum force on the shaft of an electric drive with a minimum rotation speed. In the role of the gearbox, a planetary type is used, equipped with spur gears with a small gear backlash.

There is a large selection of devices on the market that have individual characteristics and are suitable for certain areas of activity. These points must be taken into account when choosing a model.

Principle of operation

Depending on the type of unit, its design features may differ, but the general principle of operation is almost unchanged. So, the stator has four windings located at a 90-degree angle.

As soon as voltage is applied to the first winding, the rotor moves to the angle indicated above. When voltage is applied to the second, third and fourth windings, the shaft continues to rotate until it completes a full circle. Then the process is repeated from the beginning.

If you want to change the order of rotation, you need to apply pulses in the opposite direction. For convenience, users can control the stepper motor and change its characteristics, taking into account the specifics of use.

Advantages and disadvantages

Before using a stepper motor, you need to study its pros and cons. According to them, it is easier to judge the relevance of the use of equipment for solving problems of varying complexity.

Pros:

Accuracy. When voltage is applied to certain windings, the rotor rotates through a strictly defined angle.
Long service life. If you monitor the equipment, carry out periodic checks and restoration procedures, a stepper motor can last no less than a machine.
Often used as a cheaper alternative to a servo. It is often used to automate various kinds of nodes.
Stability. SD operates under different loads and is not afraid of fluctuations in this parameter.
Ease of use. Stepper motor control does not require special knowledge. Even a beginner can understand the principle of action and the rules of use.
Excellent performance: maintaining maximum torque (even at low speed), sharp fixation after stopping.
Ease of repair. It has a simple design, so there are no difficulties with maintenance and restoration.

Cons:

Low moment. Stepper motors cannot boast sufficient torque with increasing rotational speed. The only way out is to improve the dynamic parameters with the help of special PWM drivers.
Vibrations. Due to the step discreteness, vibrations arise, which inevitably lead to a decrease in the torque and the appearance of resonances in the system.
Positioning risk. Changing this parameter is possible when the load rises above the allowable parameter.
Little efficiency. A stepper motor uses a lot of power even with minimal load.
Difficulty picking up speed. The unit hardly gains momentum after an instantaneous overload.
Risk of “slippage” of the rotor. This is a known issue that occurs when the load is increased above the allowable value. To solve it, you can install a sensor or increase the power of the motor.

This is not an exhaustive list of weak and strong characteristics of a stepper mechanism, but sufficient to make a decision.

Main characteristics

When choosing a stepper motor, you need to look at its parameters.

Let’s highlight the main points:

The number of complete steps. The smoothness and accuracy of the stroke, as well as the resolution, depend on this indicator. In modern models, the number of full steps should be in the range of 200-400.
winding resistance. Indicates the voltage that the unit can produce.
Angle of discrete movement. It is calculated by dividing 360 degrees by the number of individual movements per revolution. The optimal indicator is from 0,9 to 1,8 degrees.
Phase inductance. Determines the rate of current increase, which is relevant for accelerated shaft rotation.
breakdown voltage. The maximum parameter at which the integrity of the insulating layer is violated and the safety of use is determined.
Insulation resistance. Measured between each of the windings and the casing.
Rated current. The largest parameter at which safe operation of the unit is possible.
Permissible voltage (“permanent”). The measurement is carried out on turns. Sometimes this parameter is not indicated, but in this case it can be calculated according to Ohm’s law.

It is important to pay special attention to one more parameter – the moment. It comes in several types:

holding: relevant in the event of a complete stop and current supply of two phases;
torque: depends on the speed, the maximum indicator for the unit is indicated;
locking: necessary for turning the shaft in the absence of power;
inertial: the lower this figure, the faster the engine accelerates.

A comprehensive analysis of the characteristics allows you to more accurately select a device for solving specific problems.

Connecting a stepper motor

To supply potential to the windings of the stepper motor, a mechanism is needed that is capable of delivering one or a group of pulses in a specific sequence. The role of such elements are semiconductor devices and drivers based on microprocessors.

They provide a group of output terminals, each of which forms the mode of operation and voltage supply.

Depending on the connection scheme, certain outputs of the device are used. As a result, it is possible to choose a specific rotation speed, step or microstep for moving in a plane.

In total, there are six main connection schemes:

bipolar;
bipolar with a tap from the central part of the winding;
unipolar with four phases and connection of a pair of windings;
four-phase unipolar with parallel connection;
four-phase unipolar with serial connection.

If the stepper motor is powered from the same driver, a number of features can be distinguished in relation to the circuits mentioned above:

The taps are always connected to the corresponding terminals. When the windings are connected in series, the inductance of the windings increases and the current decreases.
The user receives passport parameters regarding parameters. When connected in parallel, the current increases and the inductance decreases. If you connect the winding in one phase, the torque at low speeds decreases, and the current decreases.
The dynamic and electrical parameters are saved (taking into account the data in the passport).
Increased torque and use for high frequencies.
Torque increase (used for low speeds).

Schematic connection diagrams are shown below.

For trouble-free operation of stepper motors, it is important to remember the intricacies of supplying the rated voltage, the speed of the torque and reducing the line voltage.

Connecting a stepper motor to Arduino deserves special attention. In this case, the control outputs from the driver are connected to the digital pins on the Arduino Uno.

The supply voltage is 5 V. An additional power supply can be used to prevent overheating of the board.

By the way, how to make a smart home on Arduino read here https://elektrikexpert.ru/arduino.html.

Stepper motor control

As already noted, there are several ways to control a stepper unit. Each of the options has a number of features in the issue of signaling to the existing poles.

The main management methods include:

Wave. The peculiarity is the supply of excitation to one winding. It is to her that the rotor poles are pulled up. At the same time, the stepper motor is not able to withstand a large load, because it gives out only a part of the moment.
Full step. The essence of such control is the simultaneous excitation of two phases, which guarantees the greatest torque with a parallel connection scheme. If you connect the windings in series, the maximum current and voltage will be created.
Half step. A combination of the two modes discussed above. When implementing such a circuit in a stepper motor, voltage is applied alternately. First, it is sent to one coil, and then immediately to both. As a result, the best fixation is guaranteed at the highest speeds and the maximum number of steps.

To overcome inertia and achieve softer control, a micro-stepping structure is applied. A feature is the task of a sinusoid using numerous pulses.

As a result, the interaction forces of the magnetic circuits change more smoothly, and a smooth movement between the poles is ensured. As a result, jerks during operation are reduced.

By the presence of a controller, stepper motors are divided into two types:

Controllerless. An H-bridge circuit is used with the ability to change polarity to reverse the device. Depending on the situation, it is done on a microcircuit or transistor principle. First, voltage is applied to the bridge, and, thanks to parallel switches, current flows through the motor windings. As a result, it is possible to establish rotation in any direction.
Controller. The advantage of execution is the ability to control the stepper unit in different modes. The key element is an electronic unit that issues a group of signals and sets the sequence of their transmission. To avoid damage in the event of a short circuit or other motor failure, each output is protected by a reverse pulse diode.

The most popular are two control schemes – from a controller with a differential input and an “open collector” type output.

The first option is characterized by reliable protection against interference with the connection of the direct / inverse signal to suitable poles. Here it is necessary to shield the wire through which the signal is supplied. This is the best solution for low power devices.

The second circuit is distinguished by the connection of the “positive” outputs of the controller connected to the “positive” output. Above 9V, a resistor must be added to reduce the current. In addition, using this solution, you can set the desired number of steps in a certain speed mode and set the acceleration.

Stepper motor driver

Stepper motor control is impossible without the use of a driver – an electronic device that ensures its operation, taking into account control signals.

In other words, this is a circuit element designed to control the motor windings by applying digital signals.

Thanks to this design, the rotation of the rotor of the stepper motor is ensured. The driver works after connecting the power source, the windings of the device itself and the source of the control signal.

Depending on the type of driver, a number of additional tasks can be solved:

control of overcurrent, voltage increase and polarity reversal;
automatic current reduction in case of long idle time;
protection against the effect of back EMF;
construction of simple movement schemes without using a computer (built-in frequency generator), etc.

Structurally, the driver consists of a controller and a power unit. The first component is based on a microprocessor and can be programmed, and the second is a semiconductor power amplifier, the purpose of which is to convert the current pulses applied to the phases.

Drivers are conditionally divided into three categories (according to the type of current delivery):

Constant voltage. It supplies a high potential in turn to each of the windings. The total current depends on the resistance of the latter, and at high speeds – on the inductance. Such drivers have low efficiency and can only be used at low speeds.
Duplex. First, a voltage is applied, due to which the current in the winding rises to the desired value, after which the potential source is turned off, and the current is maintained by a low voltage source. Such drivers have higher efficiency and reduce motor heating. They work in full and half step mode.
PWM type. They are in the greatest demand due to their reliability and ease of management. Their feature is to apply a high voltage PWM signal to the winding, cut off by a small current. These drivers are intelligent and programmable.

In addition, stepper motor drivers differ in type. They are analog, digital and with an encoder. Let’s talk about them in more detail.

Analog

They are distinguished by high reliability and efficiency, due to the relatively low current consumption.

The task of such devices is to alternately supply a pulse to different stator windings, taking into account a predetermined program. This ensures a certain angle and direction of rotation.

Advantages of analog drivers:

low price;
protection against short circuit and high voltage;
automatic current reduction;
no risk of accidental overheating.

The main models include:

CW-230. Designed to control a bipolar stepper unit for two phases with a maximum current of up to 3 A. The motor can be controlled in up to 1/64 step mode. The power unit is controlled by three signals applied to the differential inputs. Pros: low price, isolation of input signals, protection against erroneous connection, short circuit and high voltage.
QJ Designed to control a bipolar stepper motor with two phases and a current limit of up to 4,5 A. Control is available in the mode up to 1/256 step. For control, three signals are used, which are fed to the inputs PUL, DIF and ENA. Thanks to this feature, you can connect to the LPT port of a PC and successfully work with the CNC machine tool program. Pros: full set of protections, automatic current reduction, isolated input signals, affordable price.
QJ6060AC – designed to control a 2-phase stepper motor. The largest current parameter is up to 6 Amperes for each of the phases. Available control from 1/128 step. Three signals are used for control (as in the model considered above). Connection of stepper motor for CNC machines and a number of plotters is available.

digital

These are more modern models that operate on the basis of a digital control signal. It is based on a 32-bit processor that enhances the performance of the equipment used.

Stepper motors working with such a driver emit a low level of vibration, minimal heating, and a small noise level.

Advantages of digital devices:

automatic setting;
high performance;
overload protection;
a larger set of functions;
maximum division by steps;
automatic voltage reduction at XX, etc.

With encoder

Such drivers are devices built on a digital principle and having a high response. They are used as a replacement for more complex control systems that require high accuracy.

Features include:

the presence of feedback;
torque and speed support;
ensuring smooth movement and low noise level;
protection against current and other overloads;
reducing the heating of the motor and ensuring its normal operation.

When using such a driver, you can not be afraid of delays while maintaining maximum performance.

Popular models include:

2HSS86H is a 2-phase digital servo driver that combines stepper and servo functions. It is used for equipment that needs high torque, speed, cost-effectiveness and stability at 0 speed. Its use guarantees smoothness and minimal noise of the stepper motor.
CWDS860H is a new generation device that combines the best qualities of servo and stepper devices. Guarantees vibration reduction, noise reduction and greater positioning accuracy. Due to its uniform operation and high response speed, this model is suitable for programs that need to move quickly over short distances and require smooth operation. Features of the model: stability at 0 speed, speed and profitability.
HBS57 is an alternative option for programs requiring high performance and increased reliability (where a servo drive is used). The system includes a 3-phase stepper and a digital high-speed driver. The device is characterized by a high reaction speed and the absence of roars. The engine heats up less, has a lower noise level and runs without delay.

DRIVER 2HSS86H

In addition to those discussed above, there are other types of drivers, but they are used less often.

What are multi-axis controllers

In simple words, multi-axis controllers are modern devices with built-in microprocessors and an integrated programmable circuit.

They are small in size and easy to operate. They are used for precise positioning of units along two or more axes.

The main field of application is the automation of a machine stepper motor equipped with multi-axis electric drives. Their feature is the support of several languages and the ability to manage online.

Controller Features:

isolated digital inputs/outputs;
high level of productivity;
support for slave/master devices;
option of remote control of the controller;
interpolation support (circular, linear);
a wide range of digital and analog inputs/outputs, Internet ports and PWM outputs.

DIY ball motor driver

If desired, a driver for a ball motor can be made independently, but subject to the purchase of the necessary equipment. First, decide what type of SHD you have in your hands.

There are only two windings in a bipolar device, so the number of outgoing wires will be four. In a unipolar motor, there are more windings, so the number of leads is appropriate.

The bipolar motor control circuit consists of several elements:

Pulse generator.
Switch.
Power keys that control the windings of motors.

The generator is assembled on the basis of the 555 chip in the usual way. Each pulse that is issued by the generator ensures that the motor moves one step.

The switch is assembled on the basis of the 4013 chip, and the power part is L239D (driver chip).

Two batteries are used as a power source, providing a voltage equal to five volts. After turning on the power, the generator delivers pulses, the frequency of which can be changed by adjusting the resistance of the generator.

Depending on the scheme used, you can use the reverse or connect the stepper motor without it.

To ensure reverse, the same chain is assembled with the difference that at the output of the switch it will be possible to change the polarity on the windings. In other words, when the connection principle is changed, the direction of rotation also changes.

In the reverse circuit, two FAN 8082 commutator motor drivers are used. After turning on the stepper motor, you can press the switch to rotate in the other direction.

Connection schemes.

Instead of a generator, you can connect a clock button, with which it is easy to avoid the bounce of contact groups. If desired, you can even count the number of steps of the motor, if necessary.

Features of the first L293D driver (for the first circuit):

Device voltage from +5 to +15 V.
Board size 60×21 mm.
The maximum current is 1,2 A, but in practice, at a current greater than 0,5 A, the circuit starts to heat up.
Combined outputs – 4, 5, 12, 13.

Features of the second FAN 8082 driver (for the second circuit):

Device voltage from +5 to +15 V.
Maximum current – 1,6 A.

Unlike the previous device, this type of driver handles the load better. If desired, as noted above, a contact bounce damper can be used.

Features of stepper motors with a gearbox: what is it, what are

Stepper motors with a gearbox are devices equipped with a cylindrical or worm additional mechanism (reducer). Let’s take a brief look at the features of each option.

With worm gear

Worm-type step motors guarantee greater torque and are actively used for CNC machines and automated production devices. The reduction ratio is from 1 to 10 to 1 to 60. The drive is included, but without the output shaft.

The worm gear is useful when it is necessary to achieve high torque at minimum angular speed.

The peculiarity of stepper motors with the type of gearbox under consideration is distinguished by the following advantages:

high efficiency;
relatively large load capacity;
minimum play of the output shaft;
stable operation in pulsating modes;
smooth running;
precise position fixation, thanks to the self-braking option;
compactness.

Devices with a worm motor have a simple design and a relatively low price. When choosing, it is necessary to take into account the reduction factor, dimensions and future mode of use.

examples:

ШД-57 mm with worm gear. They can be maintenance-free and self-braking. Supplied without output shaft. Single or input shaft can be purchased separately. Models – PL57WG76-10 (20, 40, 60) with a reduction of 1 to 10, 1 to 20, 1 to 40 and 1 to 60, respectively.
ШД-86 mm with worm gear. Here the conditions are the same as in the above variant. Models – PL86WG118-10 (20, 40, 60) with a reduction of 1 to 10, 1 to 20, 1 to 40 and 1 to 60, respectively.

With spur gear

Ball motors equipped with a spur type gearbox are standard devices having several windings, where the current supplied to any of the stator windings causes the rotor to move.

Sequential activation of the windings leads to discrete angular movements.

Features of these motors:

high efficiency;
small load capacity;
minimum backlash on the output shaft;
stable operation even in pulsating modes.

Variants of execution:

Unipolar. Budget solution built on magnets. The device is made of gears made of plastic and can be controlled by ULN Suitable for use with Arduino kits in DIY systems. Models – 28BYJ-48-12 or 28BYJ-48-5. They differ only in resistance. In the first case, 90, and in the second, 30 ohms.
SD-57 mm (NEMA 23). Ball motors for 57 m with a cylindrical gearbox. The moment on the output shaft is up to 3 N * m, and the backlash is up to 1 degree. Popular models are PL57GH76-3D8, PL57GH76-5D8, PL57GH76-10D8, PL57GH76-20D8, PL57GH76-50D8.
ShD-86 m (NEMA34). 86 mm units with backlash up to 1 degree and output torque up to 20 Nm. Popular models are PL86GH113-3D14, PL86GH113-5D14, PL86GH113-10D14, PL86GH113-20D14, PL86GH113-50D14.

Optional options: FL86STH65-2808AG3 / -BG3, FL86STH65-2808AG5 / -BG5, FL86STH65-2808AG12.5 / -BG12.5, FL86STH65-2808AG25 / -BG25, FL86STH65-2808AG50 / -BG50 and others.

Three-phase stepper motors

The main feature of 3-phase stepper motors is the ability to connect to three phases of direct current. They are used in equipment requiring more accurate positioning, minimal vibration and low noise levels. Otherwise, the scope of use of such SD is no different.

Features:

angular step – 1,2 degrees;
phase resistance – from 0,24 to 1,4 ohms;
inductance – from 0,267 to 9,82 mH.

Advantages of 3-phase stepper motors:

uniform moment;
improved acceleration and deceleration parameters;
maintaining the working torque at high speeds;
minimal noise;
low vibration.

The selection must take into account the operating current, angular step, torque, inductance and torque/speed dependence. It is also necessary to take into account the parameters of the shaft (its diameter).

Stepper motors for 3D printer

Stepper motors for 3D printers are small devices that are characterized by low weight and minimal torque. The most popular models are NEMA17, which differ in steps of 1,8 degrees. Thanks to this feature, you can more accurately adjust the positioning of the device.

When choosing a stepper motor for a 3D printer, pay attention to the following parameters:

weight and dimensions;
shaft diameter – should be suitable for a 3D printer in terms of design features;
holding moment – optimally 2,5-4 kg;
rated current – the best option is 1,7 A.

Popular models are Nema 17, 42HM34-1334 (0.9°), Nema 23, 57HS41-2804, Nema 8, 20HS38-0604, Nema 17, 42HM48-1684 (0.9°), Nema 17, 17HS4401 with 27:1 reduction gear, etc. d.

Results

The stepper motor is a versatile device with a wide range of applications and improved performance. It can be used in CNC machines, peripherals and even 3D printers. But for the right choice, you need to know a few points: features, characteristics and connection rules.

Stepper motors: what it is, where it is used, device and principle of operation, types and their design features, stepper motor driver, connection and control – ElektrikExpert.ru