{"id":3707,"date":"2018-02-10T09:09:47","date_gmt":"2018-02-10T14:09:47","guid":{"rendered":"https:\/\/dronebotworkshop.com\/?p=3707"},"modified":"2023-04-11T16:54:56","modified_gmt":"2023-04-11T20:54:56","slug":"stepper-motors-with-arduino","status":"publish","type":"post","link":"https:\/\/dronebotworkshop.com\/stepper-motors-with-arduino\/","title":{"rendered":"Stepper Motors with Arduino – Getting Started with Stepper Motors"},"content":{"rendered":"

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\"Download \"Parts<\/a> \"View<\/a> \"Download<\/a><\/p>\n

Learn how to control bipolar and unipolar stepper motors with an Arduino using drivers like ULN2003, L298N, and A4988. In this article, I’ll show you all you need to know to get started with stepper motors.<\/span><\/p>\n

Introduction<\/span><\/h2>\n

Stepper Motors are used in a wide variety of devices ranging from 3D printers and CNC machines to DVD drives, heating ducts, and even analog clocks. Yet despite their popularity, many experimenters shy away from using stepper motors as they seem to require complex hookups and code. <\/span><\/p>\n

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In this article, I hope to dispel that myth by showing you just how easy it is to use a stepper motor with an Arduino. So follow along, I promise to take you through all of this \u201ccomplex\u201d stepper theory one step at a time!<\/span><\/p>\n

Stepper Motors<\/span><\/h2>\n

Stepper motors are DC motors that rotate in precise increments or \u201csteps\u201d. They are very useful when you need to position something very accurately. They are used in 3D printers to position the printhead correctly and in CNC machines where their precision is used to position the cutting head. If your digital camera has an autofocus or remote zoom feature chances are a stepper motor is being employed to do that.<\/span><\/p>\n

\"Stepper<\/p>\n

Unlike DC motors stepper motors are controlled by applying pulses of DC electricity to their internal coils. Each pulse advances the motor by one step or by a fraction of a step, the latter is known as \u201cmicrostepping\u201d and will be explained shortly.<\/span><\/p>\n

Some users confuse stepper motors with servo motors but they are actually two different beasts. A servo motor is unique in that it\u2019s motor shaft can be moved to a precise angle, most servos only rotate 180 or 270 degrees although there are modified servos that can spin a full 360 degrees. A servo motor is \u201caware\u201d of its position and can be moved to a specific angle even if an external force moves the motor shaft.<\/span><\/p>\n

Steppers, on the other hand, are \u201cunaware\u201d of their position. \u00a0They can be moved to an exact position in reference to where they start stepping (i.e 36 degrees clockwise) but unlike servos they can be misaligned if their shaft is moved by an external force. \u00a0In many applications a servo is first moved to a \u201choming\u201d or reference position before being controlled, printers commonly do this when they are first initialized.<\/span><\/p>\n

Because the move in discrete steps a stepper motor is not often used where a smooth continuous rotation is required, However with the use of gearing and microstepping they can approach a smooth rotation and their ability to be very accurately positioned often outweighs the roughness of their movement.<\/span><\/p>\n

Another advantage stepper motors have over DC motors is the ability to move art very slow speeds without stalling, in fact, stalling really isn\u2019t a concept with stepper motors. \u00a0They also pack a lot of torque into a comparably small package.<\/span><\/p>\n

How Stepper Motors Work<\/span><\/h2>\n

Stepper motors have a magnetized geared core that is surrounded by a number of coils that act as electromagnets. Despite the number of coils electrically there really are usually only two coils in a stepper motor, divided into a number of small coils.<\/span><\/p>\n

By precisely controlling the current in the coils the motor shaft can be made to move in discrete steps, as illustrated in the following diagrams:<\/span><\/p>\n

\"Bipolar<\/p>\n

In the first diagram the coil at the top is energized by applying electricity in the polarity shown. The magnetized shaft is attracted to this coil and then locks into place.<\/span><\/p>\n

Now look what happens when the electricity is removed from the top coil and applied to the other coil. The shaft is attracted to the second coil and locks into place there.<\/span><\/p>\n

\"Bipolar<\/p>\n

The jump between the two positions is one step (in this illustration a step is 90 degrees, in actual fact, a stepper motor usually steps just a fraction of this. The diagrams are simplified for clarity).<\/span><\/p>\n

Microstepping<\/span><\/h3>\n

We have seen how the motor shaft moves to lock itself into place in front of an attracting electromagnet, each magnet represents one step. It is, however, possible to move the motor shaft into positions between steps. This is known as \u201cmicrostepping\u201d.<\/span><\/p>\n

In order to understand how microstepping works look at the next diagram:<\/span><\/p>\n

\"Bipolar<\/p>\n

In this illustration, the current has been applied to BOTH coils in an equal amount. This causes the motor shaft to lock into place halfway between the two coils. This would be known as a \u201chalf step\u201d.<\/span><\/p>\n

The principle can be extended to include quarter steps, eight steps, and even sixteenth steps. This is done by controlling the ratio of the current applied to both coils to attract the motor shaft to a position between the coils but closer to one coil than the other.<\/span><\/p>\n

By using microstepping it is possible to move the shaft of a stepper motor a fraction of a degree, allowing for extremely precise positioning.<\/span><\/p>\n

Types of Stepper Motors<\/span><\/h2>\n

Internally there are a number of ways to design a stepper motor, such as Variable Reluctance, Permanent Magnet, and Hybrid stepper motors. These design differences primarily deal with the method employed to create the magnetic field within the motor.<\/span><\/p>\n

For most experimenters, these differences will be merely academic but if you are choosing a stepper motor for a very specific design you may want to look into this more.<\/span><\/p>\n

For most users, the main difference between stepper motor design boils down to the way the coils are wired within the motor. There are two methods employed – Bipolar and Unipolar. \u00a0These two types of stepper motors are not interchangeable (although it is possible to \u201chack\u201d a Unipolar motor to create a Bipolar motor).<\/span><\/p>\n

Let\u2019s look at these two types of stepper motors.<\/span><\/p>\n

Bipolar Stepper Motors<\/span><\/h3>\n

Bipolar stepper motors consist of two coils of wire (electrically, actually split into several physical coils) and generally have four connections, two per coil. \u00a0The simplified diagrams of stepper operation that you just looked at in the previous section are all bipolar stepper motors.<\/span><\/p>\n

\"Bipolar<\/p>\n

An advantage of bipolar stepper motors is that they make use of the entire coil winding so they are more efficient. \u00a0However, they require a more complex controller or driver to operate as to reverse direction the polarity of the voltage applied to the coils needs to be reversed.<\/span><\/p>\n

Unipolar Stepper Motors<\/span><\/h3>\n

A unipolar stepper motor also consists of two coils (electrically) but each coil has a center tap so there are three connections on each coil. \u00a0This results in six connections, however many unipolar stepper motors have only five connections as the two center taps are internally connected.<\/span><\/p>\n

\"Unipolar<\/p>\n

In a unipolar stepper motor only half of each coil is used at one time. In most configurations, a positive voltage is applied to the center tap and left there. A negative voltage is then applied to one side of the coil to attract the motor shaft, as illustrated below:<\/span><\/p>\n

\"Unipolar<\/p>\n

As with the bipolar motor, the unipolar stepper motor can be made to advance one step when current is removed from the top coil and applied to one side of the second coil:<\/span><\/p>\n

\"Unipolar<\/p>\n

You can also microstep a unipolar stepper motor by using the same technique that we used with bipolar steppers, applying current to both coils.<\/span><\/p>\n

Now to reverse the direction of a unipolar motor you don\u2019t need to reverse polarity. Instead, the negative voltage is applied to the OTHER side of the coil. This causes the current to flow in the opposite direction within the coil and this, in turn, moves the motor shaft in the opposite direction.<\/span><\/p>\n

\"Unipolar<\/p>\n

Unipolar stepper motors are easier to control as there is no requirement to reverse current polarity to change direction. However, as the unipolar stepper motor only makes use of half of the coil windings at any given moment they are not as efficient as half of the wiring is essentially wasted.<\/span><\/p>\n

We will work with both unipolar and bipolar stepper motors in the experiments we are about to do.<\/span><\/p>\n

It should be noted that there are also stepper motors that can be wired as both bipolar and unipolar. These motors have four coils which can be joined to make either two center-tapped coils (for a unipolar configuration) or just two big coils (in a bipolar configuration). \u00a0\u00a0These stepper motors will have eight wires, two per coil.<\/span><\/p>\n

Reading Stepper Motor Specifications<\/span><\/h2>\n

Choosing a stepper motor can be a somewhat daunting task but it doesn\u2019t have to be. Many first time users are scared off by the vast number of specifications included with some stepper motors. In actual fact, they are not that difficult to understand.<\/span><\/p>\n

Here are a few of the key specifications you\u2019ll find included with stepper motors, along with a short definition of them:<\/span><\/p>\n

Phase: <\/b>This refers to the groupings of the individual coils in the stepper motor. A stepper motor may have several coils but they are wired together and controlled in phases. Two, Four and Five phase stepper motors are common. There will often be a phase diagram included with a stepper motor that indicates the sequence that the motor phases are driven in.<\/span><\/p>\n

Step Angle:<\/b> \u00a0This is the amount that the shaft of the motor will spin for each individual full step, measured in degrees, \u00a0In some stepper motors this is referred to as <\/span>Steps Per Revolution<\/b> and the two figures are just different ways of expressing the same thing.<\/span><\/p>\n

As an example, a common rating for a stepper motor is a 1.8-degree step angle. As there are 360 degrees in a full rotation this is equivalent to 200 steps per revolution (1.8 x 200 = 360).<\/span><\/p>\n

Voltage:<\/b> Simply the voltage rating of the motor coils. It is also a function of the current rating and the coil resistance and you can use Ohm’s Law to calculate one from the other.<\/span><\/p>\n

Current: <\/b>The maximum current at the rated voltage. This is a useful specification as it will allow you to select a suitable driver and power supply for your stepper motor.<\/span><\/p>\n

Resistance:<\/b> The coil resistance, measured in ohms.<\/span><\/p>\n

Inductance: <\/b>The inductance of each motor coils, measured in millihenries. This is an important specification as inductance will limit the maximum speed you\u2019ll be able to efficiently drive your stepper at. Typically unipolar stepper motors have an advantage here as they only use half a coil and thus have lower inductance than their bipolar equivalents.<\/span><\/p>\n

Holding Torque:<\/b> This will be the amount of force that is created when the stepper motor is energized.<\/span><\/p>\n

Detent Torque<\/b>: This is the amount of holding torque that can be expected when the motor is NOT energized.<\/span><\/p>\n

Shaft Style: <\/b>The physical shape of the motor shaft. You will need to know this in order to mate your stepper motor with gears, pulleys and other external connections such as shaft couplers. There are several common shapes used, in addition, the shaft length can be important for obvious reasons.<\/span><\/p>\n

Some common shaft types are as follows:<\/span><\/p>\n