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Arduino and Nema 17 Stepper motor using micros()

Components/How To >> Arduino and Nema 17 Stepper motor using micros()

Arduino and Nema 17 Stepper motor using micros()

As part of my DCC Turntable project I needed to use a Nema 17 stepper motor. However, because the turntable is triggered by a DCC command that is also activating servos for point control I cannot have delay() in my code as is used in most stepper motor examples.

Normally I would get round this using millis() but because of the very short periods of time involved I needed to use micros() instead. This in itself is not a problem but because the value for microseconds since the Arduino resstarted in saved in an unsigned long, the value overruns and returns to ) after about 70 minutes unlike millis() that overruns after about 50 days.

As such the timing code needs to allow for the overrun.

Circuit Diagram

For information on setting up a Nema 17 stepper motro follow the link below.

Controlling a Stepper Motor with Arduino UNO

 

Example 1: Nema17_Stepper_Test_v1.ino Conventional stepper code using delay()

Click to Download code: Nema17_Stepper_Test_v1.ino

This sketch moves the stepper motor backwards and forwards, however because it uses delay() it block the Arduino from doing anything else.
This is not a problem if the only task being performed is to control the stepper motor but if you need yourArduino to perform other tasks at the same time you will have problems.

 

 
/*Example sketch to control a stepper motor with A4988 stepper motor driver and Arduino without a library. More info: https://www.makerguides.com */
// Define stepper motor connections and steps per revolution:
#define dirPin 9
#define stepPin 8
#define stepsPerRevolution 200
void setup() {
  // Declare pins as output:
  Serial.begin(9600);
    Serial.println("a4988 stepper test");
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
}
void loop() {
  // Set the spinning direction clockwise:
  Serial.println("clock");
  digitalWrite(dirPin, HIGH);
  // Spin the stepper motor 1 revolution slowly:
  for (int i = 0; i < stepsPerRevolution; i++) {
    // These four lines result in 1 step:
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(200);
    digitalWrite(stepPin, LOW);
    delayMicroseconds(500);
  }
  
  delay(1000);
  // Set the spinning direction counterclockwise:
  digitalWrite(dirPin, LOW);
  Serial.println("anticlock");
  // Spin the stepper motor 1 revolution quickly:
  for (int i = 0; i < stepsPerRevolution; i++) {
    // These four lines result in 1 step:
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(300);
    digitalWrite(stepPin, LOW);
    delayMicroseconds(100);
  }
  delay(1000);
  
}

Example 2: Nema17MicrosV1.ino Stepper code using micros()

Click to Download code: Nema17MicrosV1.ino

This version uses micros() in a way that is not effected by the 70 minute rollover for an explanation of why try this link

Arduino Tutorial: Avoiding the Overflow Issue When Using millis() and micros()

 

 
/* Nema17MicrosV1
 *  How to control a Nema 17 stepper motor without using the delay() function
 * 
 */

const int stepPin = 8;
const int dirPin = 9;
unsigned long stepperTimer;
int currentStepperSpeedDelay = 500;//changing this value changes the stepper motor speed.
byte stepInState = 0;//high or low state for next step
int stepCounter;
const int clockwise = 0;
const int anticlockwise = 1;

int stepperDirection;//stores the current direction of rotation

void setup() {
  Serial.begin(9600);
  Serial.println("Nema17MicrosV1...");
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  digitalWrite(dirPin, clockwise); // LOW for anticlockwise
  stepperDirection = clockwise;
}

void loop() {
  unsigned long currentMicros; 
  currentMicros = micros();
  
  if ((currentMicros - stepperTimer) >= currentStepperSpeedDelay) {
      stepperTimer = currentMicros;
      if (stepInState > 0) {
        stepInState = 0;
      } else {
        stepInState = 1;
      }
      digitalWrite(stepPin, stepInState);
      stepCounter++;
  }
  //after 200 steps change direction
  if(stepCounter > 200){
   stepCounter = 0;//reset the counter
   if(stepperDirection == clockwise){
    stepperDirection == anticlockwise;
    digitalWrite(dirPin, clockwise); //change the dirPin 
   }else{
    stepperDirection == clockwise;
    digitalWrite(dirPin, clockwise); //change the dirPin 
   }
  }

}

Additional Resource Links

Controlling a Stepper Motor with Arduino UNO

Arduino Tutorial: Avoiding the Overflow Issue When Using millis() and micros()

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