1. Walmart Stepper Machine
2. Small Stepper Motors
3. Seated Stepper Machine
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5. Stepper Motor Slot Machine Parts
6. Best Stepper Machine

1) Electrical performance 2) Product Details Show 3) Main Application These stepper motor widely used in Robot, lock, Auto shutter, USB fan, Slot machine, Money. Favorites Shenzhen Ineed Youngsun Technology Co., Ltd. In electronic reel type slot machines the reels are typically positioned by stepper motors, which may be contained in removable modules within the machine. The stepper motors respond to applied signals which are progressively phase-shifted relative to each other such that the stepper motor is caused to turn one element of rotation for each progression of the phase signals.

In this post, we will discuss of stepper motor vs servo motor. before that, we need to understand the definition of both motors.

What is the stepper motor?

Stepper motor also called a step motor is a type of brushless, synchronous electromechanical device. its full rotation divided into equal parts.

What is the servo motor?

Servo motor is an electrical motor that has an inbuilt encoder for gets reading from output motion. Also, it is used for the precise control of speed, torque, and position.

Before we discuss the mechanism of stepper motor vs servo motor need to understand the open-loop and close-loop controller system.

Open-loop controller system

An open-loop controller system also called a non-feedback system, it is a type of continuous controller system. Also, it does not compare the output signal with the input signal.so this type of controller system has not any auto error correction methods.

Closed-loop controller system

This controller system gets feedback from the output signal and it compares with the input signal. If it has any problem in output signal this system automatically fixes that issue.

Now we discuss the mechanism of stepper motor vs servo motor.

Mechanism of the stepper motor.

This motor has not any sensor for gets signal from the output, so it can’t get any feedback signal from output. It also called an open-loop circuit and the motor can control without any feedback path. The Stepper motor stator field winding pole generates a rotating magnetic field. So that magnetic-field work on rotor permeate magnet and it helps rotate the motor.

Mechanism of the servo motor.

This motor has a close loop circuit so its position, speed, and acceleration control by using that feedback path and its controller circuit. Also, that feedback path can use for error detection of the output motion.

Construction

Construction of stepper motor

Stepper motor is the electromechanical device, it has rotor and stator like a normal motor. Also, this motor rotor made by using a permanent magnet or soft iron. Most Stepper motor has eight poles or more stator winding. Now we discuss eight poles motor. That poles are connected four couple of poles and each couple of pole work at a time. Also, those magnetic fields rotate through the rotor. That rotation magnetic field helps to the rotation of the motor.

Construction of servo motor

Servo motor contains a normal motor and an inbuilt sensor. This sensor design by using an encoder. This sensor can detect output motion.

Types

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Stepper motor types

1. Permanent magnet stepper motor.

This motor rotor made by using a permanent magnet, the motor rotation start by attraction or repulsion between rotor permanent magnet and starter electromagnet.

Variable reluctance stepper motor rotor design by using plain iron. The stator rotation magnetic field attraction helps to rotate the motor.

Its rotor made by the combination of permanent magnet and plain iron. This motor rotor permanent magnet covers soft iron casing. That soft iron cylinder shape rotor cover has small poles and its attraction or repulsion between stator helps the motor rotation.

Servo motor type

Servo motor type based on the power supply

1. AC servo motor.

AC servo motor is an AC motor. Most of the time it used squirrel cage induction motor. Two-phase squirrel cage induction motor used for small load

This type of motor has two separate dc power supply for field winding and armature winding. Motor control archive by changing field current or armature current.

Servo motor types based on the type of motion

1. Positional rotation servo.

This is the most common type of servo motor and its output shaft rotates only half of the cycle. That motor can rotate the shaft’s particular angle and speed.

Continuous rotation servo motor also likes positional rotation but the main difference is it can rotate full cycle. The motor control signal can change the speed and direction of the rotation.

Liner servo motor also likes the positional rotation servo motor but its use to additional gear to get circular rotation into linear motion. This motor not commonly used in industrial applications.

Speed torque performance stepper motor vs servo motor

Above the graph, stepper motor torque gets high value under 1000rpm. After increasing the speed than 1000rpm torque value goes down, but the servo motor gets constant torque value under high-speed conditions.

Compare the advantages and disadvantages of stepper motor vs servo motor

Now we discuss the Advantages of both motors

Advantages of stepper motor

• This motor hasn’t a feedback path, so this motor is simple to control than the servo motor.
• Also, the external closed-loop control system is expensive, but no need for this kind of expensive unit.
• The closed-loop control system is used advanced technology, so the skilled person needs to control that system, but no need for any person to operate stepper motor.
• Stepper motor less expensive than a servo motor that is the most important advantage of it.
• Compare with DC servo motor stepper motor is a brushless motor so it has more life and less maintains.
• It has an excellent response for starting, stopping, and reversing.
• Stepper motor speed is proportional to the input frequency of the input pulse, so it is easy to control the motion of the motor.
• Stepper motor has a large number of the electromagnetic pole, so it can get a specific stopping point for many applications.
• It is safer to use than servo motor because it takes some damage to the system motor automatically stop.
• This motor has very high torque under low speed, so it no needs any gearbox for high load.
• Stepper motor does not get damage for high load applications.

Advantages of servo motor

• Servo motor has high efficiency and less noise generation.
• Also, it has constant torque under high speed. Servo motor can get high rpm like 3000-800RPM easily with constant torque. (Modern servo motor)
• Servo motor can run smoothly than a stepper motor.
• This motor can rotate any particular angle, position, and velocity.
• It can get quickly and easily any torque for particular applications.
• Servo motor very accurate than a stepper motor, because it encoder gets feedback and error correct every time.

Now we discuss the Disadvantages of both motors

The disadvantage of stepper motor

• Under the high-speed conditions, the stepper motor gets less torque value.
• Stepper motor has less accuracy than the servo motor because it has not any error correction path, so take some time to identify an error in the system.
• Also stepper motor has less efficiency than servo motor, because, it needs a constant power supply to remember position information.

Disadvantages of servo motor

• Servo motor needs to high initial cost because its control system is more expensive. To compare with stepper need more initial cost to install the system.
• Expensive software needs to control the servo motor. Eg: PLC
• Tuning a control loop of servo motor very difficult process. It needs more time and skill person. Sometimes it will take 6 hours or more.
• Limited peak toque, a servo motor can be damaged with high load application so need to the protection circuit.
• Some times its needs gearbox for high load applications.

Applications of stepper motor vs servo motor

Applications of stepper motor

• Floppy disk driver.
• Flatbed scanner.
• Computer printers.
• Slot machine.
• Image scanner.
• Compact disk driver.
• Camera lenses.
• CNC machine.
• 3D printer.

Applications of servo motor

• Robotics.
• CNC machine.
• Automated manufacturing industries.
• Laser cutting machine.

Comparison chart

Conclusion

Comparing with both motors we can understand servo motor is more expensive and get high performance under high-speed condition than a stepper motor. But the stepper motor gets high torque under low-speed condition. Stepper motor has a self-protection method but servo motor not, so we need to understand the most suitable motor for our task. I think you can identify in our stepper motor vs servo motor tutorial.

If you are planning on building your own 3D printer or a CNC machine, you will need to control a bunch of stepper motors. And having one Arduino control all of them can take up a lot of the processing and not leave you a lot of room to do anything else; unless you use a self-contained dedicated stepper motor driver – A4988.

It can control both speed and spinning direction of a bipolar stepper motor like NEMA 17 with just two pins. How cool is that!

Do you know how stepper motors work?

The stepper motors use a cogged wheel and electromagnets to rotate the wheel one ‘step’ at a time.

Each HIGH pulse sent, energizes the coil, attracts the nearest teeth of the cogged wheel and drives the motor one step.

The way you pulse these coils greatly affects the behavior of the motor.

• The sequence of pulses determines the spinning direction of the motor.
• The frequency of the pulses determines the speed of the motor.
• The number of pulses determines how far the motor will turn.

A4988 Stepper Motor Driver Chip

At the heart of the module is a Microstepping Driver from Allegro – A4988. It’s small in stature (only 0.8″ × 0.6″) but still packs a punch.

The A4988 stepper motor driver has output drive capacity of up to 35 V and ±2A and lets you control one bipolar stepper motor at up to 2A output current per coil like NEMA 17.

The driver has built-in translator for easy operation. This reduces the number of control pins to just 2, one for controlling the steps and other for controlling spinning direction.

The driver offers 5 different step resolutions viz. full-step, half-step, quarter-step, eighth-step, and sixteenth-step.

A4988 Motor Driver Pinout

The A4988 driver has total 16 pins that interface it to the outside world. The connections are as follows:

Let’s familiarize ourselves with all the pins one by one.

Power Connection Pins

The A4988 actually requires two power supply connections.

VDD & GND is used for driving the internal logic circuitry which can be 3V to 5.5 V.

Whereas,

VMOT & GND supplies power for the motor which can be 8V to 35 V.

According to datasheet, the motor supply requires appropriate decoupling capacitor close to the board, capable of sustaining 4A.

Warning:

This driver has low-ESR ceramic capacitors on board, which makes it vulnerable to voltage spikes. In some cases, these spikes can exceed the 35V(maximum voltage rating of A4988), potentially permanently damaging the board and even the motor.

One way to protect the driver from such spikes is to put a large 100µF (at least 47µF) electrolytic capacitor across motor power supply pins.

Microstep Selection Pins

The A4988 driver allows microstepping by allowing intermediate step locations. This is achieved by energizing the coils with intermediate current levels.

For example, if you choose to drive NEMA 17 having 1.8° or 200 steps per revolution in quarter-step mode, the motor will give 800 microsteps per revolution.

The A4988 driver has three step size(resolution) selector inputs viz. MS1, MS2 & MS3 . By setting appropriate logic levels to these pins we can set the motors to one of the five step resolutions.

These three microstep selection pins are pulled LOW by internal pull-down resistors, so if we leave them disconnected, the motor will operate in full step mode.

Control Input Pins

The A4988 has two control inputs viz. STEP and DIR.

STEP input controls the mirosteps of the motor. Each HIGH pulse sent to this pin steps the motor by number of microsteps set by Microstep Selection Pins. The faster the pulses, the faster the motor will rotate.

DIR input controls the spinning direction of the motor. Pulling it HIGH drives the motor clockwise and pulling it LOW drives the motor counterclockwise.

If you just want the motor to rotate in a single direction, you can tie DIR directly to VCC or GND accordingly.

The STEP and DIR pins are not pulled to any particular voltage internally, so you should not leave them floating in your application.

Pins For Controlling Power States

The A4988 has three different inputs for controlling its power states viz. EN, RST, and SLP.

EN Pin is active low input, when pulled LOW(logic 0) the A4988 driver is enabled. By default this pin is pulled low so the driver is always enabled, unless you pull it HIGH.

SLP Pin is active low input. Meaning, pulling this pin LOW puts the driver in sleep mode, minimizing the power consumption. You can invoke this especially when the motor is not in use to conserve power.

RST is also an active low input. When pulled LOW, all STEP inputs are ignored, until you pull it HIGH. It also resets the driver by setting the internal translator to a predefined Home state. Home state is basically the initial position from where the motor starts and it’s different depending upon the microstep resolution.

TIP

The RST pin is floating. If you are not using the pin, you can connect it to the adjacent SLP/SLEEP pin to bring it high and enable the driver.

Output Pins

The A4988 motor driver’s output channels are broken out to the edge of the module with 1B, 1A, 2A & 2B pins.

You can connect any bipolar stepper motor having voltages between 8V to 35 V to these pins.

Each output pin on the module can deliver up to 2A to the motor. However, the amount of current supplied to the motor depends on system’s power supply, cooling system & current limiting setting.

Cooling System – Heatsink

Excessive power dissipation of the A4988 driver IC results in the rise of temperature that can go beyond the capacity of IC, probably damaging itself.

Even if the A4988 driver IC has a maximum current rating of 2A per coil, the chip can only supply approximately 1A per coil without getting overheated.

For achieving more than 1A per coil, a heat sink or other cooling method is required.

The A4988 driver usually comes with a heatsink. It is advisable to install it before you use the driver.

Current limiting

Before using the motor, there’s a small adjustment that we need to make. We need to limit the maximum amount of current flowing through the stepper coils and prevent it from exceeding the motor’s rated current.

There’s a small trimmer potentiometer on the A4988 driver that can be used to set the current limit. You should set the current limit to be at or lower than the current rating of the motor.

To make this adjustment there are two methods:

Method 1:

In this method we are going to set the current limit by measuring the voltage (Vref) on the “ref” pin.

1. Take a look at the datasheet for your stepper motor. Note down it’s rated current. In our case we are using NEMA 17 200steps/rev, 12V 350mA.
2. Put the driver into full-step mode by leaving the three microstep selection pins disconnected.
3. Hold the motor at a fixed position by not clocking the STEP input.
4. Measure the voltage (Vref) on the metal trimmer pot itself while you adjust it.
5. Adjust the Vref voltage using the formula

   Current Limit = Vref x 2.5

   For example, if your motor is rated for 350mA, you would adjust the reference voltage to 0.14V.

Tip:

An easy way to make adjustments is to use an alligator clip on the shaft of a metal screwdriver and attach that to your multimeter so that you can measure and adjust the voltage with the screwdriver at the same time.

Method 2:

In this method we are going to set the current limit by measuring the current running through the coil.

1. Take a look at the datasheet for your stepper motor. Note down it’s rated current. In our case we are using NEMA 17 200steps/rev, 12V 350mA.
2. Put the driver into full-step mode by leaving the three microstep selection pins disconnected.
3. Hold the motor at a fixed position by not clocking the STEP input. Do not leave the STEP input floating, connect it to logic power supply(5V)
4. Place the ammeter in series with one of the coils on your stepper motor and measure the actual current flowing.
5. Take a small screwdriver and adjust the current limit potentiometer until you reach rated current.

You will need to perform this adjustment again if you ever change the logic voltage(VDD)

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Wiring A4988 stepper motor driver with Arduino UNO

Now that we know everything about the driver, we will connect it to our Arduino.

Connections are fairly simple. Start by connecting VDD and GND(next to VDD) to the 5V and ground pins on the Arduino. DIR and STEP input pins are connected to #2 & #3 digital output pins on Arduino respectively.

connect the stepper motor to the 2B, 2A, 1A & 1B pins. Actually A4988 is conveniently laid out to match the 4-pin connector on several bipolar motors so, that shouldn’t be a problem.

Warning:

Connecting or disconnecting a stepper motor while the driver is powered can destroy the driver.

Next, Connect RST pin to the adjacent SLP/SLEEP pin to keep the driver enabled. Also keep the microstep selection pins disconnected to operate the motor in full step mode.

Finally, connect the motor power supply to the VMOT and GND pins. Remember to put a large 100µF decoupling electrolytic capacitor across motor power supply pins, close to the board.

Arduino Code – Basic Example

Seated Stepper Machine

The following sketch will give you complete understanding on how to control speed and spinning direction of a bipolar stepper motor with A4988 stepper motor driver and can serve as the basis for more practical experiments and projects.

Code Explanation:

The sketch starts with defining Arduino pins to which A4988’s STEP & DIR pins are connected. We also define stepsPerRevolution. Set this to match your stepper motor specifications.

In setup section of code, all the motor control pins are declared as digital OUTPUT.

In loop section we spin the motor clockwise slowly and then spin it counterclockwise quickly at an interval of a second.

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Control Spinning Direction: To control the spinning direction of a motor we set the DIR pin either HIGH or LOW. A HIGH input spins the motor clockwise and a LOW will spin it counterclockwise.

Control Speed: The speed of a motor is determined by the frequency of the pulses we send to the STEP pin. The higher the pulses, the faster the motor runs. A pulses is nothing but pulling the output HIGH, waiting a bit then pulling it LOW and waiting again. By changing the delay between two pulses, you change the frequency of those pulses and hence the speed of a motor.

Arduino Code – Using AccelStepper library

Controlling the stepper without a library is perfectly fine for simple, single motor applications. But when you want to control multiple steppers, you’ll need a library.

So, for our next experiment we will make use of an advanced stepper motor library called AccelStepper library. It supports:

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• Acceleration and deceleration.
• Multiple simultaneous steppers, with independent concurrent stepping on each stepper.

This library is not included in the Arduino IDE, so you will need to install it first.

Library Installation

To install the library navigate to the Sketch > Include Library > Manage Libraries… Wait for Library Manager to download libraries index and update list of installed libraries.

Filter your search by typing ‘accelstepper’. Click on the first entry, and then select Install.

Arduino Code

Here’s the simple sketch that accelerates the stepper motor in one direction and then decelerates to come to rest. Once the motor makes one revolution, it changes the spinning direction. And it keeps doing that over and over again.

Code Explanation:

We start off by including the newly installed AccelStepper library.

We define Arduino pins to which A4988’s STEP & DIR pins are connected. We also set motorInterfaceType to 1. (1 means an external stepper driver with Step and Direction pins)

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Next, we create an instance of stepper library called myStepper.

In the setup function we first set the maximum speed of the motor to a thousand. We then set an acceleration factor for the motor to add acceleration and deceleration to the movements of the stepper motor.

Next we set the regular speed of 200 and the number of steps we’re going to move it to i.e. 200 (as NEMA 17 moves 200 steps per revolution).

In the loop function, we use an If statement to check how far the motor needs to travel (by reading the distanceToGo property) until it reaches the target position (set by moveTo). Once distanceToGo reaches zero we will move the motor in the opposite direction by changing the moveTo position to the negative of its current position.

Now at the bottom of the loop you’ll notice we have called a run() function. This is the most important function, because the stepper will not run until this function is executed.