Arduino UNO and ADXL345 record jumps height and hang time when kitesurfing

Projects Programming
1

I'm trying this prodject with Arduino UNO and ADXL345,

The problem is that i get this read out in seriell monitor:

Reset
3.72 -0.10 -0.23 Reset
Reset time
Reset
Reset time
Reset
Reset time
Reset
-8.12 0.10 0.35 Reset
2.83 -0.10 -0.94 Reset
Reset time

I'm only interested in getting the jump height displayed in meters is this possibel with this code?

/* ============================================
Uses I2Cdev device library : http://www.i2cdevlib.com
*/

// Arduino Wire library is required if I2Cdev I2CDEV_ARDUINO_WIRE implementation
// is used in I2Cdev.h
#include "Wire.h"

// I2Cdev and ADXL345 must be installed as libraries, or else the .cpp/.h files
// for both classes must be in the include path of your project
#include "I2Cdev.h"
#include "ADXL345.h"

// Declare objects
ADXL345 accel;

// Defines
#define G_MS2 9.80665

void setup() {
// join I2C bus (I2Cdev library doesn't do this automatically)
Wire.begin();

Serial.begin( 115200 );

// Initialize device and setup
Serial.println( "Initializing I2C devices..." );
accel.initialize();
accel.setRate( ADXL345_RATE_200 );
accel.setRange( ADXL345_RANGE_2G );

// verify connection
Serial.println( "Testing device connections..." );
Serial.println( accel.testConnection() ? "ADXL345 connection successful" : "ADXL345 connection failed" );
}

void loop() {
// Variables declaration
float ax, ay, az, speedZOld, speedZThreshold, speedZ, positionZ, speedDelta;

unsigned long timerAccumulation, timerSerial; // the timer
unsigned long INTERVAL = 5; // the repeat interval
unsigned long INTERVAL_SERIAL = 2000;
unsigned long i;

speedZOld = 0;
speedZ = 0;
positionZ = 0;
speedDelta = 0;
speedZThreshold = 0.1;

// Start timers
timerAccumulation = millis();
timerSerial = timerAccumulation;

Serial.println( "\t\tStarting main loop" );

while (1) {

// Compute data
i = millis()-timerAccumulation;
if ( i > INTERVAL ) {
timerAccumulation += INTERVAL; // Reset timer
az = accel.getAccelerationZ();
az = (az-231) * G_MS2 / 256.0; // Convertion to m/s2
speedZ += az * i/1e3; // Integration to get speed
// distance moved in deltaTime, s = 1/2 a t^2 + vt
double sz = 0.5 * az * i * i/1e6 + speedZ * i/1e3;
positionZ += sz;
}

if ( abs( speedZ ) < speedZThreshold ) { // If speed is behind given threshold, discard it to avoid noise accumulation
if ( abs( speedZOld ) > speedZThreshold ) { // If previous speed was high, it was moving
if ( abs( positionZ ) > 0.15 ) { // If we moved more than 0.15 cm, display it
Serial.print( az ); Serial.print( "\t" );
Serial.print( speedZ ); Serial.print( "\t" );
Serial.print( positionZ );
}
positionZ = 0;
speedZ = 0;
Serial.println( "\tReset" );
}
}
speedZOld = speedZ;

if ( (millis()-timerSerial) > INTERVAL_SERIAL ) { // Periodic reset to clear values from noise
Serial.println( "\tReset time" );
timerSerial += INTERVAL_SERIAL;
positionZ = 0;
speedZ = 0;
}

}
}

Please Help.

2

The problem is that i get this read out in seriell monitor:

Why is that a problem? If it truly is, why don't you print more?

3

Way do i get - values on the printing?...i Rise the accelerometer exactly the same hight everytime and the Readings are very different every time. Wish one of the values are supsed to be the highet in meters?

4

getting the jump height displayed in meters is this possibel with this code?

Not at all. Consumer grade accelerometers are too inaccurate and noisy to be used for distance estimation, plus there are other problems as explained here.

For height measurements, you could use an altimeter based on an air pressure sensor.

Please use code tags when posting code.

5

Kitesurfing is in water.......how is it possible to reed whit the altimeter in water?

6

The kitesurfer is in the air, especially when jumping.

7

Yes you are right...but when you fall it can wet....can you get readings if you have it in a waterproufe house or plastic bag?

8

The air pressure is atmospheric pressure, inside and outside a plastic bag.

However, a rigid, perfectly sealed waterproof housing can't be used with a pressure sensor to measure altitude. You would need to put a tiny hole it.