Possible noise from the motors

Hi Everyone,

I’m trying to control a self-balancing car, but it seems that the MPU6050 get dirty once my motors operate a full velocity.
I’m controlling my motors with the module L298N and with the PWM signal (pin 5, 6, 9 and 10 from the arduino).
I have read about decoupling it, with capacitors, but I don’t know exactly how should I do it.

This is my code. It’s a little messy (sorry for that, it just I’m still figuring out what is going on) and also an image of my project:

#include <PID_v1.h>
#include <LMotorController.h>
#include "I2Cdev.h"
#include "MPU6050_6Axis_MotionApps20.h"

#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
#include "Wire.h"
#endif

#define MIN_ABS_SPEED 20

MPU6050 mpu;

#define DEBUG
//#define OFFSET_1


//#define STOP


// MPU control/status vars
bool dmpReady = false; // set true if DMP init was successful
uint8_t mpuIntStatus; // holds actual interrupt status byte from MPU
uint8_t devStatus; // return status after each device operation (0 = success, !0 = error)
uint16_t packetSize; // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount; // count of all bytes currently in FIFO
uint8_t fifoBuffer[64]; // FIFO storage buffer

// orientation/motion vars
Quaternion q; // [w, x, y, z] quaternion container
VectorFloat gravity; // [x, y, z] gravity vector
float euler[3]; // [psi, theta, phi]    Euler angle container

//PID
//double originalSetpoint = 175.8;
#ifdef OFFSET_1
      double originalSetpoint = 225;
#else
      double originalSetpoint = 184;
#endif 
    

double setpoint = originalSetpoint;
double movingAngleOffset = 0.1;
double input, output, output_left, output_right, error;
int moveState=0; //0 = balance; 1 = back; 2 = forth
double Kp = 40;
double Kd = 0.05;
double Ki = 5;
PID pid(&input, &output, &setpoint, Kp, Ki, Kd, DIRECT);

double motorSpeedFactorLeft = 1;
double motorSpeedFactorRight = 1;
double motorSpeedFactorForward = 1;
double motorSpeedFactorBackward = 1;

//MOTOR CONTROLLER
int ENA = 5;
int IN1 = 6;
int IN2 = 7;
int IN3 = 8;
int IN4 = 9;
int ENB = 10;
//LMotorController motorController(ENA, IN1, IN2, ENB, IN3, IN4, motorSpeedFactorLeft, motorSpeedFactorRight);

//timers
long time1Hz = 0;
long time5Hz = 0;

volatile bool mpuInterrupt = false; // indicates whether MPU interrupt pin has gone high
void dmpDataReady()
{
  mpuInterrupt = true;
}


void setup()
{

  
  // join I2C bus (I2Cdev library doesn't do this automatically)
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
  Wire.begin();
  Wire.setClock(400000);  // Set the SCL clock speed to 400kHz
  //Wire.setClock(200000);  // Set the SCL clock speed to 400kHz
  //TWBR = 24; // 400kHz I2C clock (200kHz if CPU is 8MHz)
#elif I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_FASTWIRE
  Fastwire::setup(400, true);
  //Fastwire::setup(200, true);
#endif

  Serial.begin(115200);
  mpu.initialize();

  devStatus = mpu.dmpInitialize();

  // supply your own gyro offsets here, scaled for min sensitivity

  #ifdef OFFSET_1
      mpu.setXGyroOffset(0);
      mpu.setYGyroOffset(0);
      mpu.setZGyroOffset(0);
      mpu.setZAccelOffset(16372); 
      mpu.setYAccelOffset(5); 
      mpu.setXAccelOffset(2); 
    #else
      mpu.setXGyroOffset(-52);
      mpu.setYGyroOffset(-12);
      mpu.setZGyroOffset(53);
      mpu.setZAccelOffset(2420); 
      mpu.setYAccelOffset(2881); 
      mpu.setXAccelOffset(-784); 
    #endif  

  // make sure it worked (returns 0 if so)
  if (devStatus == 0)
  {

    //mpu.CalibrateAccel(6);
    //mpu.CalibrateGyro(6);
    // turn on the DMP, now that it's ready
    mpu.setDMPEnabled(true);

    // enable Arduino interrupt detection
    attachInterrupt(0, dmpDataReady, RISING);
    mpuIntStatus = mpu.getIntStatus();

    // set our DMP Ready flag so the main loop() function knows it's okay to use it
    dmpReady = true;

    // get expected DMP packet size for later comparison
    packetSize = mpu.dmpGetFIFOPacketSize();

    pid.SetMode(AUTOMATIC);
    pid.SetSampleTime(10);
    pid.SetOutputLimits(-255, 255);  
  }
  else
  {
    // ERROR!
    // 1 = initial memory load failed
    // 2 = DMP configuration updates failed
    // (if it's going to break, usually the code will be 1)
    Serial.print(F("DMP Initialization failed (code "));
    Serial.print(devStatus);
    Serial.println(F(")"));
  }

  
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);

  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);

  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  
}
void loop()
{
  #ifdef STOP
      return;
  #endif 
  
  // if programming failed, don't try to do anything
  if (!dmpReady) return;

  // wait for MPU interrupt or extra packet(s) available
  while (!mpuInterrupt && fifoCount < packetSize)
  {
    pid.Compute();  

    output = 255;
    output_left = output * motorSpeedFactorLeft;
    output_right = output * motorSpeedFactorRight;
    if(input > (setpoint))
    { 
      output_left = output_left*motorSpeedFactorForward ;
      output_right = output_right* motorSpeedFactorForward;
      
      Move_Forward();  
    }
    else if(input < (setpoint))
    {
      output_left = output_left*motorSpeedFactorBackward ;
      output_right = output_right* motorSpeedFactorBackward;
      Move_Backward();
    }
    else
    {
      Stop();
    }                
  }
  // reset interrupt flag and get INT_STATUS byte
  mpuInterrupt = false;
  mpuIntStatus = mpu.getIntStatus();

  // get current FIFO count
  fifoCount = mpu.getFIFOCount();

  // check for overflow (this should never happen unless our code is too inefficient)
  if ((mpuIntStatus & 0x10) || fifoCount == 1024)
  {
    // reset so we can continue cleanly
    mpu.resetFIFO();
    Serial.println(F("FIFO overflow!"));

    // otherwise, check for DMP data ready interrupt (this should happen frequently)
  }
  else if (mpuIntStatus & 0x02)
  {
    // wait for correct available data length, should be a VERY short wait
    while (fifoCount < packetSize) fifoCount = mpu.getFIFOCount();

    // read a packet from FIFO
    mpu.getFIFOBytes(fifoBuffer, packetSize);

    // track FIFO count here in case there is > 1 packet available
    // (this lets us immediately read more without waiting for an interrupt)
    fifoCount -= packetSize;

    mpu.dmpGetQuaternion(&q, fifoBuffer);
    mpu.dmpGetGravity(&gravity, &q);
    mpu.dmpGetYawPitchRoll(euler, &q, &gravity);
    input = (euler[1] * 180 / M_PI + 180);
    error = input - setpoint;
//    Serial.print("\tOutput: ");
//    Serial.print(output);   
    Serial.print("\tError: ");   
    Serial.println(error);
    
      
  }
}

void Move_Forward() //Code to rotate the wheel forward 
{

  
  //******RIGHT******//
      analogWrite(5, -1*output_right);
      analogWrite(6, 0);

  //******LEFT******//
      analogWrite(9, -1*output_left);
      analogWrite(10, 0);
      
      
      digitalWrite(11, HIGH); 
      digitalWrite(12, LOW);
}


void Move_Backward() //Code to rotate the wheel forward 
{
  //******RIGHT******//
      analogWrite(5, LOW);
      analogWrite(6, 1*output_right);
      
  //******LEFT******//
      analogWrite(9, 0);
      analogWrite(10, 1*output_left);

      digitalWrite(11, LOW);  
      digitalWrite(12, HIGH); 
}

void Stop() //Code to rotate the wheel forward 
{
      analogWrite(11, LOW);  
      analogWrite(12, LOW);  
      analogWrite(5, LOW);
      analogWrite(6, LOW);

      digitalWrite(9, LOW);
      digitalWrite(10, LOW);
}

OP image

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Here is how to connect capacitors to a motor to decouple motor noise.

motor caps.jpg

The L298 drivers are ancient and inefficient technology. They are ill suited for battery power projects as they waste a lot of power as heat. Pololu (and others) have modern, much more efficient drivers at low cost.