 # How to start programming with gy 521 and stepper motor for self balancing robot?

I am new and fresh beginner in Arduino and robotics so need help that how

GY 521 module gives values?

I know it gives in angular velocity for gyro and acceleration in for accelerometer.

then we calculate roll , pitch and yaw with some trigonometric formulas. OK

but then though

Why are Roll /PITCH/YAW values are changing ?

If in roll,pitch and yaw which are also constantly changing how we can program it with stepper motor? //Serial output is given in below attachment //as we can see that all three values are changing

Code is as given below(this is code for mesuring pitch,roll and yaw):-

``````/*
Arduino and MPU6050 Accelerometer and Gyroscope Sensor Tutorial
by Dejan, https://howtomechatronics.com

AccErrorX: 3.55
07:09:40.273 -> AccErrorY: 15.26
07:09:40.273 -> GyroErrorX: -3.10
07:09:40.273 -> GyroErrorY: 1.25
07:09:40.309 -> GyroErrorZ: 0.93

AccErrorX: 3.31
07:36:01.262 -> AccErrorY: 4.82

*/
#include <Wire.h>
const int MPU = 0x68; // MPU6050 I2C address
float AccX, AccY, AccZ;
float GyroX, GyroY, GyroZ;
float accAngleX, accAngleY, gyroAngleX, gyroAngleY, gyroAngleZ;
float roll, pitch, yaw;
float AccErrorX, AccErrorY, GyroErrorX, GyroErrorY, GyroErrorZ;
float elapsedTime, currentTime, previousTime;
int c = 0;
void setup() {
Serial.begin(19200);
Wire.begin();                      // Initialize comunication
Wire.beginTransmission(MPU);       // Start communication with MPU6050 // MPU=0x68
Wire.write(0x6B);                  // Talk to the register 6B
Wire.write(0x00);                  // Make reset - place a 0 into the 6B register
Wire.endTransmission(true);        //end the transmission
/*
// Configure Accelerometer Sensitivity - Full Scale Range (default +/- 2g)
Wire.beginTransmission(MPU);
Wire.write(0x1C);                  //Talk to the ACCEL_CONFIG register (1C hex)
Wire.write(0x10);                  //Set the register bits as 00010000 (+/- 8g full scale range)
Wire.endTransmission(true);
// Configure Gyro Sensitivity - Full Scale Range (default +/- 250deg/s)
Wire.beginTransmission(MPU);
Wire.write(0x1B);                   // Talk to the GYRO_CONFIG register (1B hex)
Wire.write(0x10);                   // Set the register bits as 00010000 (1000deg/s full scale)
Wire.endTransmission(true);
delay(20);
*/
// Call this function if you need to get the IMU error values for your module
calculate_IMU_error();
delay(20);
}
void loop() {
// === Read acceleromter data === //
Wire.beginTransmission(MPU);
Wire.endTransmission(false);
Wire.requestFrom(MPU, 6, true); // Read 6 registers total, each axis value is stored in 2 registers
//For a range of +-2g, we need to divide the raw values by 16384, according to the datasheet
AccX = (Wire.read() << 8 | Wire.read()) / 16384.0; // X-axis value
AccY = (Wire.read() << 8 | Wire.read()) / 16384.0; // Y-axis value
AccZ = (Wire.read() << 8 | Wire.read()) / 16384.0; // Z-axis value
// Calculating Roll and Pitch from the accelerometer data
accAngleX = (atan(AccY / sqrt(pow(AccX, 2) + pow(AccZ, 2))) * 180 / PI) - 0.58; // AccErrorX ~(0.58) See the calculate_IMU_error()custom function for more details
accAngleY = (atan(-1 * AccX / sqrt(pow(AccY, 2) + pow(AccZ, 2))) * 180 / PI) + 1.58; // AccErrorY ~(-1.58)
// === Read gyroscope data === //
previousTime = currentTime;        // Previous time is stored before the actual time read
currentTime = millis();            // Current time actual time read
elapsedTime = (currentTime - previousTime) / 1000; // Divide by 1000 to get seconds
Wire.beginTransmission(MPU);
Wire.write(0x43); // Gyro data first register address 0x43
Wire.endTransmission(false);
Wire.requestFrom(MPU, 6, true); // Read 4 registers total, each axis value is stored in 2 registers
GyroX = (Wire.read() << 8 | Wire.read()) / 131.0; // For a 250deg/s range we have to divide first the raw value by 131.0, according to the datasheet
// Correct the outputs with the calculated error values
GyroX = GyroX + 3.13; // GyroErrorX ~(-0.56)
GyroY = GyroY - 1.19; // GyroErrorY ~(2)
GyroZ = GyroZ - 0.95; // GyroErrorZ ~ (-0.8)
// Currently the raw values are in degrees per seconds, deg/s, so we need to multiply by sendonds (s) to get the angle in degrees
gyroAngleX = gyroAngleX + GyroX * elapsedTime; // deg/s * s = deg
gyroAngleY = gyroAngleY + GyroY * elapsedTime;
yaw =  yaw + GyroZ * elapsedTime;
// Complementary filter - combine acceleromter and gyro angle values
roll = 0.96 * gyroAngleX + 0.04 * accAngleX;
pitch = 0.96 * gyroAngleY + 0.04 * accAngleY;

// Print the values on the serial monitor
Serial.print(roll);
Serial.print("/");
Serial.print(pitch);
Serial.print("/");
Serial.println(yaw);
}
void calculate_IMU_error() {
// We can call this funtion in the setup section to calculate the accelerometer and gyro data error. From here we will get the error values used in the above equations printed on the Serial Monitor.
// Note that we should place the IMU flat in order to get the proper values, so that we then can the correct values
// Read accelerometer values 200 times
while (c < 200) {
Wire.beginTransmission(MPU);
Wire.write(0x3B);
Wire.endTransmission(false);
Wire.requestFrom(MPU, 6, true);
AccErrorX = AccErrorX + ((atan((AccY) / sqrt(pow((AccX), 2) + pow((AccZ), 2))) * 180 / PI));
AccErrorY = AccErrorY + ((atan(-1 * (AccX) / sqrt(pow((AccY), 2) + pow((AccZ), 2))) * 180 / PI));
c++;
}
//Divide the sum by 200 to get the error value
AccErrorX = AccErrorX / 200;
AccErrorY = AccErrorY / 200;
c = 0;
// Read gyro values 200 times
while (c < 200) {
Wire.beginTransmission(MPU);
Wire.write(0x43);
Wire.endTransmission(false);
Wire.requestFrom(MPU, 6, true);
GyroErrorX = GyroErrorX + (GyroX / 131.0);
GyroErrorY = GyroErrorY + (GyroY / 131.0);
GyroErrorZ = GyroErrorZ + (GyroZ / 131.0);
c++;
}
//Divide the sum by 200 to get the error value
GyroErrorX = GyroErrorX / 200;
GyroErrorY = GyroErrorY / 200;
GyroErrorZ = GyroErrorZ / 200;
// Print the error values on the Serial Monitor
Serial.print("AccErrorX: ");
Serial.println(AccErrorX);
Serial.print("AccErrorY: ");
Serial.println(AccErrorY);
Serial.print("GyroErrorX: ");
Serial.println(GyroErrorX);
Serial.print("GyroErrorY: ");
Serial.println(GyroErrorY);
Serial.print("GyroErrorZ: ");
Serial.println(GyroErrorZ);
}
``````

Then How we can interact it with stepper motor? with position on Holding for self balancing 2 wheeler robot?

I will like to start from small specific program like stepper motor ( nima 17 , A4988 Driver) with 12 to 5 volt power supply used for TWO WHEEL SELF BALNCING ROBOT (Arduino Nano) and circuit given as:-  