Introduction

An accelerometer is the device which measure proper acceleration.A proper acceleration is not the 3-coordinate axis values(rate of change of velocity) of any moving object.An accelerometer will measure an acceleration due to earth's gravity,straight towards the g=9.81m/s2.There are various application of accelerometer in science and industry. Sensitive accelerometers are used into the navigation systems for aircraft and missiles.It also measure the vibration of a rotating object.

In this work I use accelerometer to find gesture up,down,left and right gesture of any moving object.To implement it with Intel Edison board I have used MMA7660 3-Axis Digital Accelerometer Grooove connector.You need to connect the device with the I2C port of the groove connector of the Intel Edison board.

Here is the following hardware(digital Accelerometer) connection on the Intel Edison board groove connector

Using the code

It generates the different acceleration values for different gestures towards x,y and z axis.Through these values you can recognize gestures.These values are not constant but most of the time for one gesture for example left gesture it generates same values for example x=0 y=1 z=1.I have used javascript(node.js) to implement the above concept.This is the following code.

var mqtt=require('mqtt');
var client  = mqtt.connect('mqtt://iot.eclipse.org');
var topic='rupam/edison/gesture';

var digitalAccelerometer = require('jsupm_mma7660');

var myDigitalAccelerometer = new digitalAccelerometer.MMA7660(

 digitalAccelerometer.MMA7660_I2C_BUS,

digitalAccelerometer.MMA7660_DEFAULT_I2C_ADDR);

myDigitalAccelerometer.setModeStandby();

myDigitalAccelerometer.setSampleRate(digitalAccelerometer.MMA7660.AUTOSLEEP_64);

myDigitalAccelerometer.setModeActive();

var ax, ay, az;

ax = digitalAccelerometer.new_floatp();

ay = digitalAccelerometer.new_floatp();

az = digitalAccelerometer.new_floatp();

var outputStr;

var myInterval = setInterval(function()

{

myDigitalAccelerometer.getAcceleration(ax, ay, az);

outputStr = "Acceleration: x = "

+ roundNum(digitalAccelerometer.floatp_value(ax), 6)

+ " y = " + roundNum(digitalAccelerometer.floatp_value(ay), 6)

+ " z = " + roundNum(digitalAccelerometer.floatp_value(az), 6);

console.log(outputStr);

if(x==1 && y==0 && z==1)
{

console.log("Up…………….");
client.publish(topic, 'UP');
}

if(x==1 && y==0 && z==0)
{
console.log("down…………...");
client.publish(topic, 'DOWN');
}
if(x==0 && y==0 && z==1)
{
console.log("Straight……………..");
client.publish(topic, 'STRAIGHT');

}
if(x==0 && y==1 && z==1)
{
console.log("left……………...");
client.publish(topic, 'LEFT');
}
if(x==1 && y==1 && z==1)
{
console.log("right………….");
client.publish(topic, 'RIGHT');
}

},500);

//to display the acceleration upto a certain decimal places

function roundNum(num, decimalPlaces)

{

var extraNum = (1 / (Math.pow(10, decimalPlaces) * 1000));

return (Math.round((num + extraNum)

* (Math.pow(10, decimalPlaces))) / Math.pow(10, decimalPlaces));

}

The code is developed based on the snippet here.

In the above code UPM module for the MMA7660 I2C 3-axis digital accelerometer have been used.The module name is jsupm_mma7660 for the 3 axis digital Accelerometer.Instantiate an MMA7660 on I2C bus 0 and place the device in standby mode using setModeStandby() method so we can write registers.Enable 64 samples per second and place the device into active mode using setModeActive() method.I declare a function setInterval to get proper acceleration towards x-axis,y-axis and z-axis.These values have been used to recognize gestures.

These are the following outputs:

This is the straight position:

                  Figure :Straight position

The position is recognized on the terminal is as follows:

In order to recognize a up gesture the hardware position will be placed as follows: