How do i make my DC motors run simultaneously? Im coding an adafruit motor shield for  3 DC motors to go forward &amp; backwards, and so my concern is why only my motor3 is running the whole time and motors 1 &amp; 2 are switching off meaning 1 goes than 2 goes and on and on? My code is below if you see where my mistake is in the code can you just tell me what it is and what to do to make them run simultaneously?
#include &lt;AFMotor.h&gt;
AF_DCMotor motor1(1);
AF_DCMotor motor2(2);
AF_DCMotor motor(3);

void setup() {
  Serial.begin(9600);           // set up Serial library at 9600 bps
  Serial.println(&quot;Motor test!&quot;);
  // turn on motor
  motor1.setSpeed(300);
  motor2.setSpeed(200);
  motor.setSpeed(500);
  motor.run(RELEASE);
}

void loop() {
  uint8_t i;

  //third motor
  Serial.print(&quot;tick&quot;);
  motor.run(FORWARD);
  for (i=0; i&lt;255; i++) {
    motor2.setSpeed(i);  
    delay(10);
  }
  for (i=255; i!=0; i--) {
    motor2.setSpeed(i);  
    delay(10);
  }

  //second motor
  Serial.print(&quot;tick&quot;);
  motor2.run(FORWARD);
  for (i=0; i&lt;255; i++) {
    motor2.setSpeed(i);  
    delay(10);
  }
  for (i=255; i!=0; i--) {
    motor2.setSpeed(i);  
    delay(10);
  }
  Serial.print(&quot;tack&quot;);
  motor2.run(BACKWARD);
  for (i=0; i&lt;255; i++) {
    motor2.setSpeed(i);  
    delay(10);
  }
  for (i=255; i!=0; i--) {
    motor2.setSpeed(i);  
    delay(10);
  }

  Serial.print(&quot;tick&quot;);
  motor1.run(FORWARD);
  for (i=0; i&lt;255; i++) {
    motor1.setSpeed(i);  
    delay(10);
  }
  for (i=255; i!=0; i--) {
    motor1.setSpeed(i);  
    delay(10);
  }
  Serial.print(&quot;tack&quot;);
  motor1.run(BACKWARD);
  for (i=0; i&lt;255; i++) {
    motor1.setSpeed(i);  
    delay(10);
  }
  for (i=255; i!=0; i--) {
    motor1.setSpeed(i);  
    delay(10);
  }
}
Start with the BlinkWithoutDelay example code and make modifications to suit your needs.
This is the original code.
    /*
  Blink without Delay

  Turns on and off a light emitting diode (LED) connected to a digital pin,
  without using the delay() function. This means that other code can run at the
  same time without being interrupted by the LED code.

  The circuit:
  - Use the onboard LED.
  - Note: Most Arduinos have an on-board LED you can control. On the UNO, MEGA
    and ZERO it is attached to digital pin 13, on MKR1000 on pin 6. LED_BUILTIN
    is set to the correct LED pin independent of which board is used.
    If you want to know what pin the on-board LED is connected to on your
    Arduino model, check the Technical Specs of your board at:
    https://www.arduino.cc/en/Main/Products

  created 2005
  by David A. Mellis
  modified 8 Feb 2010
  by Paul Stoffregen
  modified 11 Nov 2013
  by Scott Fitzgerald
  modified 9 Jan 2017
  by Arturo Guadalupi

  This example code is in the public domain.

  http://www.arduino.cc/en/Tutorial/BlinkWithoutDelay
*/

// constants won't change. Used here to set a pin number:
const int ledPin =  LED_BUILTIN;// the number of the LED pin

// Variables will change:
int ledState = LOW;             // ledState used to set the LED

// Generally, you should use &quot;unsigned long&quot; for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0;        // will store last time LED was updated

// constants won't change:
const long interval = 1000;           // interval at which to blink (milliseconds)

void setup() {
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // here is where you'd put code that needs to be running all the time.

  // check to see if it's time to blink the LED; that is, if the difference
  // between the current time and last time you blinked the LED is bigger than
  // the interval at which you want to blink the LED.
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis &gt;= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }

    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);
  }
}


Here are the changes that cause the LED to light up for 500 ms, then go dark for 5000 ms.
The changes are marked by // *************.
Hopefully, this will get you the idea about how to use millis() to control a device at desired intervals.
        /*
          Blink without Delay
          http://www.arduino.cc/en/Tutorial/BlinkWithoutDelay
        */

        const int ledPin =  LED_BUILTIN;                        // the number of the LED pin

    //  int ledState = LOW;                    // ************* // change this assignment as follows

        int ledState = 0;                      // ************* // ledState used as a state counter

        unsigned long previousMillis = 0;

    //  const long interval = 1000;            // ************* // change the interval as follows

        const long interval =  500;            // ************* // use a 500 ms interval

        void setup() {
          pinMode(ledPin, OUTPUT);
        }

        void loop() {
          unsigned long currentMillis = millis();
          
          if (currentMillis - previousMillis &gt;= interval) {

            previousMillis = currentMillis;    // ************* // program arrives here every 500 ms

    //      if (ledState == LOW) {             // ************* // this code is not needed
    //        ledState = HIGH;                 // ************* 
    //      } else {                           // ************* 
    //        ledState = LOW;                  // ************* 
    //      }                                  // *************

    //      digitalWrite(ledPin, ledState);    // *************


            if (ledState == 0 ) {              // *************
                digitalWrite(ledPin, HIGH);    // ************* // turn on LED at start of cycle
            }                                  // *************
            else if (ledState == 1 ) {         // *************
                digitalWrite(ledPin, LOW);     // ************* // turn off LED at end of 500 ms
            }                                  // *************
            
            ledState++;                        // ************* // increment state counter
            if (ledState &gt; 10 )  ledState = 0; // ************* // reset ledState when it has reached end of cycle
            
          }                                                     // end of if
        }                                                       // end of loop