GrabDuck

Arduino - StepperSpeedControl

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Stepper motors, due to their unique design, can be controlled to a high degree of accuracy without any feedback mechanisms. The shaft of a stepper, mounted with a series of magnets, is controlled by a series of electromagnetic coils that are charged positively and negatively in a specific sequence, precisely moving it forward or backward in small "steps".

There are two types of steppers, Unipolars and Bipolars, and it is very important to know which type you are working with. For each of the motors, there is a different circuit. The example code will control both kinds of motors. See the unipolar and bipolar motor schematics for information on how to wire up your motor.

In this example, a potentiometer (or other sensor) on analog input 0 is used to control the rotational speed of a stepper motor using the Arduino Stepper Library. The stepper is controlled by with digital pins 8, 9, 10, and 11 for either unipolar or bipolar motors.

The Arduino or Genuino board will connect to a U2004 Darlington Array if you're using a unipolar stepper or a SN754410NE H-Bridge if you have a bipolar motor.

For more information about the differences of the two types, please take a look at Tom Igoe's page on stepper motors.

Hardware Required

  • Arduino or Genuino Board
  • 10k ohm potentiometer
  • stepper motor
  • U2004 Darlington Array (if using a unipolar stepper)
  • SN754410ne H-Bridge (if using a bipolar stepper)
  • power supply appropriate for your particular stepper
  • hook-up wires
  • breadboard

Circuits

Below you'll find circuits for both unipolar and bipolar steppers. In either case, it is best to power your stepper motors from an external supply, as they draw too much to be powered directly from your Arduino board.

In both circuits, connect a 10k pot to power and ground, with it's wiper outputting to analog pin 0.

Note: Both circuits below are four wire configurations. Two wire configurations will not work with the code provided.

Unipolar Stepper Circuit and schematic

Unipolar Motor Knob Circuit

image developed using Fritzing. For more circuit examples, see the Fritzing project page

Unipolar Motor Knob Schematic

Bipolar Stepper Circuit and schematic

Code

For both unipolar and bipolar steppers

/*
Stepper Motor Control - speed control

 This program drives a unipolar or bipolar stepper motor.
The motor is attached to digital pins 8 - 11 of the Arduino.
A potentiometer is connected to analog input 0.

 The motor will rotate in a clockwise direction. The higher the potentiometer value,
the faster the motor speed. Because setSpeed() sets the delay between steps,
you may notice the motor is less responsive to changes in the sensor value at
low speeds.

 Created 30 Nov. 2009
Modified 28 Oct 2010
by Tom Igoe

 */

#include <Stepper.h>

const int stepsPerRevolution = 200 ;   // change this to fit the number of steps per revolution
// for your motor

// initialize the stepper library on pins 8 through 11:
Stepper myStepper (stepsPerRevolution , 8 , 9 , 10 , 11 ) ;

int stepCount = 0 ;   // number of steps the motor has taken

void setup ( ) {
// nothing to do inside the setup
}

void loop ( ) {
// read the sensor value:
int sensorReading = analogRead (A0 ) ;
// map it to a range from 0 to 100:
int motorSpeed = map (sensorReading , 0 , 1023 , 0 , 100 ) ;
// set the motor speed:
if (motorSpeed > 0 ) {
myStepper. setSpeed (motorSpeed ) ;
// step 1/100 of a revolution:
myStepper. step (stepsPerRevolution / 100 ) ;
}
}

See also