make 2 DC Motors the same speed with ArduinoNano

Other Hardware Motors, Mechanics, Power and CNC
1

So I have a project running, where I'm building a driving robot controlled with an app (from MIT App Inventor 2) via Bluetooth (I am using the HC-05).
The robot is driving forwards, backwards and sideways, but my 2 DC motors aren't the same speed. How can I fix this in the code? I was thinking about a new slider in the App controlling the difference of the speeds, but I am unsure how to put this in my code
I would appreciate it, if someone could help me.

int order;

// Motor A - RIGHT
int Dir_A1 = 4;
int Dir_A2 = 5;
int En_A = 6;

// Motor B - LEFT
int Dir_B1 = 7;
int Dir_B2 = 8;
int En_B = 9;

// How much gas is given
int mengeGas = 120;

// Whether gas is on
boolean gasStatus = false;

void setup() {
  
  Serial.begin(9600);

  pinMode(En_A, OUTPUT);
  pinMode(Dir_A1, OUTPUT);
  pinMode(Dir_A2, OUTPUT);

  pinMode(En_B, OUTPUT);
  pinMode(Dir_B1, OUTPUT);
  pinMode(Dir_B2, OUTPUT);

  // Vehicle is switched to "Forward" - but does not drive away
  richtungVorwaerts();
}

// change of direction

void richtungRueckwaerts() {
  // Motor 1 backwards
  digitalWrite(Dir_A1, HIGH);
  digitalWrite(Dir_A2, LOW);

  // Motor 2 backwards
  digitalWrite(Dir_B1, HIGH);
  digitalWrite(Dir_B2, LOW);
}

void richtungVorwaerts() {
  // Motor 1 forwards
  digitalWrite(Dir_A1, LOW);
  digitalWrite(Dir_A2, HIGH);

  // Motor 2 forwards
  digitalWrite(Dir_B1, LOW);
  digitalWrite(Dir_B2, HIGH);
}

// Steering left
void lenkeLinks() {
  // Right engine at full power - steers left
  // The car keeps spinning until a new order arrives.
  while (Serial.available() == false) {
    analogWrite(En_A, 135);
    analogWrite(En_B, 0);
  }
}

// Steering Right
void lenkeRechts() {
 /* Left motor at half power - steers right
    Half the power, because the left motor is about twice as powerful
    is as fast as the right one
    and all at a similar speed
    have to turn

    The car keeps spinning until a new
    Command is there.
  */

  while (Serial.available() == false) {
    analogWrite(En_B, 150);
    analogWrite(En_A, 0);
  }
}

//Car steps on the gas 
void gas() {
  if (mengeGas <= 15) {
    analogWrite(En_A, 0);
    analogWrite(En_B, 0);
  }
  else {
    int mengeGasRechts = mengeGas + 50;
    if (mengeGasRechts > 255) {
      analogWrite(En_A, 255);
      analogWrite(En_B, 250);
    }
    else {
      analogWrite(En_A, mengeGasRechts);
      analogWrite(En_B, mengeGas);
    }
  }
  gasStatus = true;
}

// Car stops
void bremse() {
  analogWrite(En_A, 0);
  analogWrite(En_B, 0);
  gasStatus = false;
}

// Reads the entries in the app
void loop() {

  if (Serial.available() > 0) {
    order = Serial.read();
  }

  if (order >= 10) {
    mengeGas = order;
    if (gasStatus == true) {
      gas();
    }
    delay(200);
  }

  if (order == 2) {
    lenkeRechts();
  }

  if (order == 3) {
    lenkeLinks();
  }

  if (order == 4) {
    gas();
  }

  if (order == 5) {
    bremse();
  }

  if (order == 6) {
    richtungVorwaerts();
  }

  if (order == 7) {
    richtungRueckwaerts();
  }
}
2

What method do you have to measure the actual rotation speed of the motors? In the REAL world, no two things can ever remain in sync without feedback and control.

Paul

3

I didn't measure them, I saw they weren't the same speed when I let the robot drive. The right motor rotates much faster..

4

dinehier:
I didn't measure them, I saw they weren't the same speed when I let the robot drive. The right motor rotates much faster..

Does that mean you want to watch the motors and manually adjust the speed? If so, why the Arduino forum?

Paul