Accelerometer ambiguous results

[bsnayak]

Hello ,

I have recently bought some sensors ADXL337 and ADXL 377 from Sprakfun. I have connected both the sensors with Arduino Mega KIIT. I am using the sample code given in Github. Here is it .

// Declaration of all necessary header file
// Inspired with example file of Sparkfun ADXL337/377
#include "Wire.h" 
#include <SPI.h> 

// Declarations of Parameters 
int scale_ADXL337 = 3;  // 3 (±3g) for ADXL337, 200 (±200g) for ADXL377
int scale_ADXL377 = 200;// 3 (±3g) for ADXL337, 200 (±200g) for ADXL377
float rawX_ADXL337, rawY_ADXL337, rawZ_ADXL337;  // Raw values for each axis of Sensor ADXL337
float rawX_ADXL377, rawY_ADXL377, rawZ_ADXL377;  // Raw values for each axis of Sensor ADXL377
float scaledX_ADXL337, scaledY_ADXL337, scaledZ_ADXL337; // Scaled values for each axis of Sensor ADXL337
float scaledX_ADXL377, scaledY_ADXL377, scaledZ_ADXL377; // Scaled values for each axis of Sensor ADXL377

boolean micro_is_5V = false; // Set to true if using a 5V microcontroller such as the Arduino Uno, false if using a 3.3V microcontroller, this affects the interpretation of the sensor data

void setup()
{
  // Initialize serial communication at 115200 baud
  Serial.begin(115200);
  Serial.print("The Accelerometer ADXL377 and ADXL337 are connected to the MEGA BOARD");
  Serial.println();
}

// Read, scale_ADXL337, and print accelerometer data
void loop()
{
  // Get raw accelerometer data for each axis
  rawX_ADXL377 = analogRead(A0);
  rawY_ADXL377 = analogRead(A1);
  rawZ_ADXL377 = analogRead(A2);
  
  rawX_ADXL337 = analogRead(A3);
  rawY_ADXL337 = analogRead(A4);
  rawZ_ADXL337 = analogRead(A5);
  
  scaledX_ADXL377 = mapf(rawX_ADXL377, 0, 1023, -scale_ADXL377, scale_ADXL377);
  scaledY_ADXL377 = mapf(rawY_ADXL377, 0, 1023, -scale_ADXL377, scale_ADXL377);
  scaledZ_ADXL377 = mapf(rawZ_ADXL377, 0, 1023, -scale_ADXL377, scale_ADXL377);
 
  
  scaledX_ADXL337 = mapf(rawX_ADXL337, 0, 1023, -scale_ADXL337, scale_ADXL337);
  scaledY_ADXL337 = mapf(rawY_ADXL337, 0, 1023, -scale_ADXL337, scale_ADXL337);
  scaledZ_ADXL337 = mapf(rawZ_ADXL337, 0, 1023, -scale_ADXL337, scale_ADXL337);
 
  

  Serial.println();
  Serial.println("--------------------------------------------------------------------");
    
  // Print out raw X,Y,Z accelerometer readings of ADXL337
  Serial.print("X_377: "); Serial.println(rawX_ADXL337);
  Serial.print("Y_377: "); Serial.println(rawY_ADXL337);
  Serial.print("Z_377: "); Serial.println(rawZ_ADXL337);
  Serial.println();
  
  // Print out scaled X,Y,Z accelerometer readings of ADXL337
  Serial.print("Scaled_X_377: "); Serial.print(scaledX_ADXL337); Serial.println(" g");
  Serial.print("Scaled_Y_377: "); Serial.print(scaledY_ADXL337); Serial.println(" g");
  Serial.print("Scaled_Z_377: "); Serial.print(scaledZ_ADXL337); Serial.println(" g");
  Serial.println();
  
  
  // Print out raw X,Y,Z accelerometer readings of ADXL337
  Serial.print("X_337: "); Serial.println(rawX_ADXL337);
  Serial.print("Y_337: "); Serial.println(rawY_ADXL337);
  Serial.print("Z_337: "); Serial.println(rawZ_ADXL337);
  Serial.println();
  
  // Print out scaled X,Y,Z accelerometer readings of ADXL337
  Serial.print("Scaled_X_337: "); Serial.print(scaledX_ADXL337); Serial.println(" g");
  Serial.print("Scaled_Y_337: "); Serial.print(scaledY_ADXL337); Serial.println(" g");
  Serial.print("Scaled_Z_337: "); Serial.print(scaledZ_ADXL337); Serial.println(" g");
  Serial.println();
  
  Serial.println("--------------------------------------------------------------------\n");

 
  
  
  delay(250); // Minimum delay of 2 milliseconds between sensor reads (500 Hz)
  
}

// Same functionality as Arduino's standard map function, except using floats
float mapf(float x, float in_min, float in_max, float out_min, float out_max)
{
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

However the output of this code is as follows.

X_377: 362.00
Y_377: 339.00
Z_377: 419.00

Scaled_X_377: -0.88 g
Scaled_Y_377: -1.01 g
Scaled_Z_377: -0.54 g

X_337: 362.00
Y_337: 339.00
Z_337: 419.00

Scaled_X_337: -0.88 g
Scaled_Y_337: -1.01 g
Scaled_Z_337: -0.54 g

--------------------------------------------------------------------


--------------------------------------------------------------------
X_377: 361.00
Y_377: 339.00
Z_377: 419.00

Scaled_X_377: -0.88 g
Scaled_Y_377: -1.01 g
Scaled_Z_377: -0.54 g

X_337: 361.00
Y_337: 339.00
Z_337: 419.00

Scaled_X_337: -0.88 g
Scaled_Y_337: -1.01 g
Scaled_Z_337: -0.54 g

--------------------------------------------------------------------

Here is the result in X UP, X Down, Y UP, Y Down, Z UP, Z Down

X UP

X_377: 362.00
Y_377: 339.00
Z_377: 421.00

Scaled_X_377: -0.88 g
Scaled_Y_377: -1.01 g
Scaled_Z_377: -0.53 g

X_337: 362.00
Y_337: 339.00
Z_337: 421.00

Scaled_X_337: -0.88 g
Scaled_Y_337: -1.01 g
Scaled_Z_337: -0.53 g


X down

X_377: 364.00
Y_377: 342.00
Z_377: 420.00

Scaled_X_377: -0.87 g
Scaled_Y_377: -0.99 g
Scaled_Z_377: -0.54 g

X_337: 364.00
Y_337: 342.00
Z_337: 420.00

Scaled_X_337: -0.87 g
Scaled_Y_337: -0.99 g
Scaled_Z_337: -0.54 g



Y up 

X_377: 364.00
Y_377: 343.00
Z_377: 420.00

Scaled_X_377: -0.87 g
Scaled_Y_377: -0.99 g
Scaled_Z_377: -0.54 g

X_337: 364.00
Y_337: 343.00
Z_337: 420.00

Scaled_X_337: -0.87 g
Scaled_Y_337: -0.99 g
Scaled_Z_337: -0.54 g



Y down 

X_377: 361.00
Y_377: 339.00
Z_377: 421.00

Scaled_X_377: -0.88 g
Scaled_Y_377: -1.01 g
Scaled_Z_377: -0.53 g

X_337: 361.00
Y_337: 339.00
Z_337: 421.00

Scaled_X_337: -0.88 g
Scaled_Y_337: -1.01 g
Scaled_Z_337: -0.53 g



Z up 


X_377: 361.00
Y_377: 338.00
Z_377: 421.00

Scaled_X_377: -0.88 g
Scaled_Y_377: -1.02 g
Scaled_Z_377: -0.53 g

X_337: 361.00
Y_337: 338.00
Z_337: 421.00

Scaled_X_337: -0.88 g
Scaled_Y_337: -1.02 g
Scaled_Z_337: -0.53 g



Z down 


X_377: 339.00
Y_377: 342.00
Z_377: 282.00

Scaled_X_377: -1.01 g
Scaled_Y_377: -0.99 g
Scaled_Z_377: -1.35 g

X_337: 339.00
Y_337: 342.00
Z_337: 282.00

Scaled_X_337: -1.01 g
Scaled_Y_337: -0.99 g
Scaled_Z_337: -1.35 g

I am not sure, if it is correct (?????????). I would expect the Acceleration in the Z direction to be nearly 1g. However it is showing in the Y direction net accelration is nearly 1g. If the sensors are damaged or should i manupulate the analog pins in the X,Y,Z directions??