Mais Informações visite: http://forum.arduino.cc/index.php?topic=225776.0 ou https://www.rcgroups.com/forums/showthread.php?2197784-DIY-vibration-meter-for-propeller-or-motor-balancing-%28etc-%29-Arduino-MMA7361

Vibration Meter - LCD out.ino

// Vibration meter
// v1.0, June 2014
// GrMis - RCGROUPS
// Mais Informações visite: http://forum.arduino.cc/index.php?topic=225776.0 ou https://www.rcgroups.com/forums/showthread.php?2197784-DIY-vibration-meter-for-propeller-or-motor-balancing-%28etc-%29-Arduino-MMA7361

#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>  // F Malpartida's NewLiquidCrystal library
 
#define I2C_ADDR    0x20  // I2C for PCF8574A inside the MJKDZ
 
#define  LED_OFF  0
#define  LED_ON  1
 
//mjkdz i2c LCD board
LiquidCrystal_I2C lcd(I2C_ADDR, 4, 5, 6, 0, 1, 2, 3, 7, NEGATIVE);
 
const int Pin_ACC_X=0; 
const int Pin_ACC_Y=1; 
const int Pin_ACC_Z=2; 
int ax,ay,az;
double a2;
double ma2;
long int last_LCD=0;
long int last_acc=0;
bool led_on=false;

double MX=0,MY=0,MZ=0;
const double c1=0.002;// 1.0/c1 is the time scale for computing the average acceleration, in milli seconds.
const double c2=0.015;// 1.0/c2 is the time scale for computing the average vibration, in milli seconds.
const double scale=1.5/512;
double AX,AY,AZ;

int count=0;

void setup() {
  delay(100);    
  lcd.begin (16,2);  // Initialize the LCD (16 characters  & 2 lines )
  lcd.setBacklight(LED_OFF);
  lcd.setCursor(0,0);
  lcd.print("Vibration meter");
  delay(1500);
  lcd.clear();
  
  analogReference(EXTERNAL);// 3.3 volts connected to aref.
 // Initialize the average accceleration vector by some initial measurement 
  MX=  1.0*analogRead(Pin_ACC_X);
  MY=  1.0*analogRead(Pin_ACC_Y);
  MZ=  1.0*analogRead(Pin_ACC_Z);  
}
 
void loop() {
 
if (micros()-last_acc>=900) {
      last_acc=micros();
      ax=  analogRead(Pin_ACC_X);//-512+20;
      ay=  analogRead(Pin_ACC_Y);//-512-30;
      az=  analogRead(Pin_ACC_Z);//-512+70;  
  
      // MX,MY,XZ are the components of the average acceleration
      MX=c1*ax+(1.-c1)*MX;
      MY=c1*ay+(1.-c1)*MY;
      MZ=c1*az+(1.-c1)*MZ;
    
// AX,AY,AZ are the components of the deviation from the average acceleration
    AX=1.0*ax-MX;  
    AY=1.0*ay-MY;  
    AZ=1.0*az-MZ;  
    
    //Square of the deviation
    a2= AX*AX+AY*AY+AZ*AZ;
    //ma2 is the average of the square of the deviation
    ma2=c2*a2+(1.-c2)*ma2;
    //count++;
}
    if (millis()-last_LCD>=300) {
      last_LCD=millis();  
      lcd.clear();
      const double g=sqrt(ma2)*scale;
        lcd.setCursor(0,0);lcd.print("|dA|=");lcd.print(g,3);
      //lcd.setCursor(0,1);lcd.print("Sampl.:");lcd.print(1.0*count/0.3,0);lcd.print("Hz");
      //count=0;
      if (g>2) {//Shake !
          led_on=!led_on;
          if (led_on)   {lcd.setBacklight(LED_ON);} else {lcd.setBacklight(LED_OFF);}
      }
   }
  }

Vibration Meter - no output.ino

// Vibration meter
// v1.0, June 2014
// GrMis - RCGROUPS

#define  LED_OFF  0
#define  LED_ON  1

const int Pin_ACC_X=0; 
const int Pin_ACC_Y=1; 
const int Pin_ACC_Z=2; 
int ax,ay,az;
double a2;
double ma2;

long int last_acc=0;
bool led_on=false;

double MX=0,MY=0,MZ=0;
const double c1=0.002;// 1.0/c1 is the time scale for computing the average acceleration, in milli seconds.
const double c2=0.015;// 1.0/c2 is the time scale for computing the average vibration, in milli seconds.
const double scale=1.5/512;
double AX,AY,AZ;

int count=0;

void setup() {
  delay(100);    

  analogReference(EXTERNAL);// 3.3 volts connected to aref.
  // Initialize the average accceleration vector by some initial measurement 
  MX=  1.0*analogRead(Pin_ACC_X);
  MY=  1.0*analogRead(Pin_ACC_Y);
  MZ=  1.0*analogRead(Pin_ACC_Z);  
}
 
void loop() {
 
  if (micros()-last_acc>=900) {
      last_acc=micros();
      ax=  analogRead(Pin_ACC_X);//-512+20;
      ay=  analogRead(Pin_ACC_Y);//-512-30;
      az=  analogRead(Pin_ACC_Z);//-512+70;  
  
      // MX,MY,XZ are the components of the average acceleration
      MX=c1*ax+(1.-c1)*MX;
      MY=c1*ay+(1.-c1)*MY;
      MZ=c1*az+(1.-c1)*MZ;
    
    // AX,AY,AZ are the components of the deviation from the average acceleration
    AX=1.0*ax-MX;  
    AY=1.0*ay-MY;  
    AZ=1.0*az-MZ;  
    
    //Square of the deviation
    a2= AX*AX+AY*AY+AZ*AZ;
    //ma2 is the average of the square of the deviation
    ma2=c2*a2+(1.-c2)*ma2;
    //count++;
  }
  if ((sqrt(ma2)*scale)>2) //Shake !
     digitalWrite(LED13,!led_on);
}