Hey! I am using an MPU6050 and want to engage the brake for our motor when there is any sudden acceleration in any direction - x,y, or z. Do I have to take the resultant? How do I calculate the slope (rate of change) between two values so that the Arduino can sense that there has been a sudden "unwanted jolt" and cuts off power to the motor?
Here is some code to start:
// defining the pins
const int dirPin = 4;
const int stepPin = 3;
const int buttonPin = 10; // the number of the pushbutton pin
const int stepsPerRevolution = 200;
//Setting up the accelerometer - allows access MPU6050 related functions in the library
/*
#include <Adafruit_MPU6050.h>
#include <Adafruit_Sensor.h>
*/
#include <MPU6050_tockn.h>
#include <Wire.h>
MPU6050 mpu6050(Wire);
long timer = 0;
//Adafruit_MPU6050 mpu;
int buttonState;
void setup() {
Serial.begin(9600);
Wire.begin();
mpu6050.begin();
mpu6050.calcGyroOffsets(true);
Serial.println();
// initialize the pushbutton pin as an input:
pinMode(buttonPin, INPUT);
// Declare pins as Outputs
pinMode(stepPin, OUTPUT);
pinMode(dirPin, OUTPUT);
}
/*
// set accelerometer range to +-8G
mpu.setAccelerometerRange(MPU6050_RANGE_8_G);
// set gyro range to +- 500 deg/s
mpu.setGyroRange(MPU6050_RANGE_500_DEG);
// set filter bandwidth to 21 Hz
mpu.setFilterBandwidth(MPU6050_BAND_21_HZ);
delay(100);
*/
void loop() {
/*
// Get new sensor events with the readings
sensors_event_t a, g, temp;
mpu.getEvent(&a, &g, &temp);
// Print out acceleration values
Serial.print("Acceleration X: ");
Serial.print(a.acceleration.x);
Serial.print(", Y: ");
Serial.print(a.acceleration.y);
Serial.print(", Z: ");
Serial.print(a.acceleration.z);
Serial.println(" m/s^2");
Serial.print("Rotation X: ");
Serial.print(g.gyro.x);
Serial.print(", Y: ");
Serial.print(g.gyro.y);
Serial.print(", Z: ");
Serial.print(g.gyro.z);
Serial.println(" rad/s");
Serial.begin(9600);
Wire.begin();
mpu6050.begin();
mpu6050.calcGyroOffsets(true);
Serial.println();
mpu6050.update();
if (millis () - timer > 200){
Serial.print(mpu6050.getAngleX());
Serial.Print (",");
Serial.print(mpu6050.getAccAngleY());
Serial.Print (",");
Serial.print(mpu6050.getAccAngleZ());
timer = millis ();
}
*/
// Set motor direction clockwise
digitalWrite(dirPin, HIGH);
buttonState = digitalRead(buttonPin);
if (buttonState == LOW) // if button is pressed, the motor will turn
//digitalWrite(stepPin, HIGH)
for (int i = 0; i < stepsPerRevolution; i++) {
// These four lines result in 1 step:
digitalWrite(stepPin, HIGH);
delayMicroseconds(450);
digitalWrite(stepPin, LOW);
delayMicroseconds(450);
}
if (buttonState == HIGH) // if button is not pressed, turn the motor off
digitalWrite(stepPin, LOW);
}
I also have this code from an Arduino library that reads the accelerometer data.
#include <MPU6050_tockn.h>
#include <Wire.h>
MPU6050 mpu6050(Wire);
long timer = 0;
void setup() {
Serial.begin(9600);
Wire.begin();
mpu6050.begin();
mpu6050.calcGyroOffsets(true);
}
void loop() {
mpu6050.update();
if(millis() - timer > 1000){
Serial.println("=======================================================");
Serial.print("temp : ");Serial.println(mpu6050.getTemp());
Serial.print("accX : ");Serial.print(mpu6050.getAccX());
Serial.print("\taccY : ");Serial.print(mpu6050.getAccY());
Serial.print("\taccZ : ");Serial.println(mpu6050.getAccZ());
Serial.print("gyroX : ");Serial.print(mpu6050.getGyroX());
Serial.print("\tgyroY : ");Serial.print(mpu6050.getGyroY());
Serial.print("\tgyroZ : ");Serial.println(mpu6050.getGyroZ());
Serial.print("accAngleX : ");Serial.print(mpu6050.getAccAngleX());
Serial.print("\taccAngleY : ");Serial.println(mpu6050.getAccAngleY());
Serial.print("gyroAngleX : ");Serial.print(mpu6050.getGyroAngleX());
Serial.print("\tgyroAngleY : ");Serial.print(mpu6050.getGyroAngleY());
Serial.print("\tgyroAngleZ : ");Serial.println(mpu6050.getGyroAngleZ());
Serial.print("angleX : ");Serial.print(mpu6050.getAngleX());
Serial.print("\tangleY : ");Serial.print(mpu6050.getAngleY());
Serial.print("\tangleZ : ");Serial.println(mpu6050.getAngleZ());
Serial.println("=======================================================\n");
timer = millis();
}
}
Compare the just now obtained values with the last set of measurements to make decisions. It should help to calculate the ratio (change in acceleration)/(time difference).
Avoid printing between successive measurements, as printing takes variable amounts of time and makes direct comparisons difficult.
To treat each axis separately in C/C++, something like this would work (assuming you are interested in either large acceleration or large deceleration):
if (fabs (Xacc_now - Xacc_last))/time_between_measurements) > some_limit ) take_action();
if (fabs (Yacc_now - Yacc_last))/time_between_measurements) > some_limit ) take_action();
if (fabs (Zacc_now - Zacc_last))/time_between_measurements) > some_limit ) take_action();
If time_between_measurements is a constant, division is not required.
You can also combine all of the above into a big, ugly "if" statement using logical or
if (
fabs (Xacc_now - Xacc_last)/time_between_measurements > some_limit or
fabs (Yacc_now - Yacc_last)/time_between_measurements > some_limit or
fabs (Xacc_now - Xacc_last)/time_between_measurements > some_limit
) take_action();
Forum members strongly recommend to start with the minimum code required to detect something of interest and get that working to your satisfaction, before adding in anything else like motor control.
Hey! I am using an MPU6050 and want to stop the NEMA 17 Steppermotor when there is any sudden acceleration in any direction - x,y, or z. I am having trouble getting the slope and the resultant to work to detect this rapid change
Here is some code to start:
/*
Accelerometer code - Automatic shutoff of NEMA 17 Stepper Motor
April 1, 2024
*/
#include <MPU6050_tockn.h> // Include the MPU6050 library
#include <Wire.h> // Include the Wire library for I2C communication
MPU6050 mpu6050(Wire); // Initialize the MPU6050 object with the Wire library
const int dirPin = 3; // Define the pin for stepper motor direction control
const int stepPin = 4; // Define the pin for stepper motor step control
const int buttonPin = 13; // Define the pin for the pushbutton
const int stepsPerRevolution = 200; // Define the number of steps per revolution for the stepper motor
long timer = 0; // Initialize a variable to store the current time
float prevAccX = 0; // Initialize a variable to store the previous X-axis acceleration
float prevAccY = 0; // Initialize a variable to store the previous Y-axis acceleration
float prevAccZ = 0; // Initialize a variable to store the previous Z-axis acceleration
bool rapidChangeDetected = false; // Initialize a flag to indicate if a rapid change in acceleration is detected
void setup() {
Serial.begin(9600); // Start serial communication at 9600 baud rate
Wire.begin(); // Initialize the I2C communication
mpu6050.begin(); // Initialize the MPU6050 sensor
mpu6050.calcGyroOffsets(true); // Calibrate the gyroscope offsets
pinMode(buttonPin, INPUT); // Set the button pin as input
pinMode(stepPin, OUTPUT); // Set the step pin for the stepper motor as output
pinMode(dirPin, OUTPUT); // Set the direction pin for the stepper motor as output
}
void loop() {
mpu6050.update(); // Update MPU6050 sensor readings
// Read acceleration values
float accX = mpu6050.getAccX(); // Read X-axis acceleration
float accY = mpu6050.getAccY(); // Read Y-axis acceleration
float accZ = mpu6050.getAccZ(); // Read Z-axis acceleration
Serial.println("=======================================================");
Serial.print("temp : ");Serial.println(mpu6050.getTemp());
Serial.print("accX : ");Serial.print(mpu6050.getAccX());
Serial.print("\taccY : ");Serial.print(mpu6050.getAccY());
Serial.print("\taccZ : ");Serial.println(mpu6050.getAccZ());
// Check for rapid change in acceleration
if (millis() - timer > 1000) { // Check if it's time to check for a rapid change
float deltaX = abs(accX - prevAccX); // Calculate change in X-axis acceleration
float deltaY = abs(accY - prevAccY); // Calculate change in Y-axis acceleration
float deltaZ = abs(accZ - prevAccZ); // Calculate change in Z-axis acceleration
float deltaAcc = sqrt(deltaX * deltaX + deltaY * deltaY + deltaZ * deltaZ); // Calculate total change in acceleration
if (deltaAcc > 0.3) { // Check if rapid change in acceleration exceeds threshold
rapidChangeDetected = true; // Set flag to indicate rapid change detected
float timeDiff = (millis() - timer) / 1000.0; // Calculate time difference since last check
float slope = deltaAcc / timeDiff; // Calculate slope of acceleration change
Serial.print("Slope: "); // Print slope to serial monitor
Serial.println(slope);
}
prevAccX = accX; // Update previous X-axis acceleration
prevAccY = accY; // Update previous Y-axis acceleration
prevAccZ = accZ; // Update previous Z-axis acceleration
timer = millis(); // Update timer to current time
}
// Set motor direction clockwise
digitalWrite(dirPin, HIGH); // Set direction pin to control motor direction
// Read button state
int buttonState = digitalRead(buttonPin); // Read state of pushbutton
// Rotate motor if button is pressed and no rapid change detected
if (buttonState == LOW ) { // Check if button is pressed and no rapid change detected
for (int i = 0; i < stepsPerRevolution &&rapidChangeDetected; i++) { // Loop for specified number of steps per revolution
digitalWrite(stepPin, HIGH); // Set step pin to high to trigger a step
delayMicroseconds(450); // Delay to control step timing
digitalWrite(stepPin, LOW); // Set step pin back to low
delayMicroseconds(450); // Delay to control step timing
}
if (buttonState == HIGH) // if button is not pressed, turn the motor off
digitalWrite(stepPin, LOW);
} else { // Stop motor if rapid change detected
digitalWrite(stepPin, LOW); // Set step pin low to stop the motor
rapidChangeDetected = false; // Reset the flag
}
}
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