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MMA7361 Accelerometer Arduino Tutorial

Now let us learn about one of the most commonly used and best accelerometer module for Arduino and Raspberry Pi – MMA7361

Have you ever played Asphalt racing game in mobile phone in which you can control the car by tilting your mobile phone. Have you ever used your phone as a compass to see in which direction you are heading. Have you  ever used Google map and notice the map rotating when you turn in one direction. Have you ever thought of how your phone is doing that? Your phone is doing all that using combined input from 3 sensors – the accelerometer,  gyro sensor and magnetometer.

In this arduino tutorial, I will be explaining accelerometer and how it can be used to make your own projects.

AccelerometerImage result for mobile accelerometer

What is an accelerometer? Simply speaking accelerometer is a device which can be used to measure with scenes in acceleration due to gravity. Using this we can calculate acceleration tilt and vibration of a device which is connected to the accelerometer.

How Does an Accelerometer Work?

Just before I mentioned accelerometer can be used to measure the tilt of an object. How can something measure the tilt of an object by just observing the acceleration due to gravity?

WeImage result for accelerometerll this is how it works. When an object is at rest in perfectly horizontal position the only force acting on it will be the acceleration due to gravity which is vertically downwards; say y axis. At this time the force on other directions, that is x axis and z axis will be zero.

When this object is tilted 45 degree, a part of acceleration due to gravity will be exerted on the x-axis. As it continues to rotate in that direction,  acceleration due to gravity in y axis decreases and x axis increases. When the object is vertical the force acting on y axis will be zero and whole force will be exerted in the x-axis. By measuring the acceleration due to gravity in the three Axis es we can measure the tilt of an object.

Using a single sensor we can only measure the acceleration in one direction. To get a complete picture of the tilt of the object, we must use three senses which will measure the acceleration in all the three directions.

Applications

Accelerometers are widely used in electronics,  in robots such as self balancing robot, humanoid robots, automatic leveller etc.  they are also used in aircrafts, rockets and guidance systems in missiles. Take out your smartphone and tilt the phone in one direction and you will see the screen orientation changes. This is also the work of accelerometer.

Gyro Sensor

Even though accelerometer can be used to measure the tilt of an object it is not good for measuring the rotation. This is where gyro sensors come to play. Gyro Sensors are devices which can be used to measure the angular velocity of an object. Gyro sensors are sometimes known as angular rate sensor or angular velocity sensor.

Gyro sensors are often used along with accelerometer to provide a complete picture of the motion of an object in 6 degree of freedom;  three degrees in lateral movement and three degrees in angular moment. these 6 values can provide an accurate picture of the object for perfect motion tracking.

There are mainly Three Types of gyroscopes available – The Rotary gyroscope , Vibrational structure gyroscope and Optical gyroscope. All of them uses different methods to calculate the angular velocity  but the output is the same.

In this post, we will be focusing on Accelerometer.

MMA7361 Accelerometer Sensor Module

MMA7361mma7361 tutorial

MMA7361 is one of the best accelerometer for Arduino and Raspberry Pi. This is an accelerometer module which is designed to work with microcontrollers. They are really easy to connect and get the readings out of it. These accelerometers have three axis of measurement- the X axis, Y axis and Z axis. In the centre of the Breakout board you can see a tiny chip. This is the chip that does all the work. This accelerometer does all its work by consuming very less power which makes it suitable for battery powered applications. There is an inbuilt voltage regulator so that even if we power the boat with 5 volt, regulator will convert it into 3.3 volt which the chipset will be used for its working.

You will get this Accelerometer for cheap price from here.

Why MMA7361?

I choose this accelerometer module because it is really cheap and is easily available in online stores such as banggood Amazon eBay etc. This accelerometer module is very easy to connect with microcontrollers such as PIC, Arduino and even with Raspberry Pi or other single board computers.

Another reason I chose this board is we can power this accelerometer with 5 volt as well as 3.3 volt. This is really useful when we are using a low powered board such as arduino MKR series boards or Raspberry Pi whose GPI opens are designed to work with a maximum of 3.3 volt.

There are two detection range of sensitivity That is + or – 1.5 G And + or – 6 G which can be easily selected using one of the pins on the board.

There is also a free fall output pin which can be used to detect free fall.

MMA7361 with Arduino Nano

So now you know what an accelerometer is, what the outputs look like and the working of MMA7361 accelerometer module. Now we are going to connect this accelerometer to arduino Nano and read the outputs in the serial monitor.

Here, I will be using an Arduino Uno to get the readings out of the MMA7361.

Connections

Connections are pretty simple. You can power the MMA7361 directly from +5V vout from the Arduino. Connect ground of accelerometer to the ground of Arduino. Connect X, Y and Z output of Accelerometer to analog pins A0, A1 and A2 of the Arduino Nano.

Code

Shown below is a simple code which can be used to read the raw analog readings from the three output pins of the accelerometer, store it in variables and display them on the serial monitor.

int x;
int y;
int z;
void setup()
{ 
Serial.begin(9600);
}
void loop()
{
x = analogRead(A0);
y = analogRead(A1);
z = analogRead(A2);
Serial.print("X = ");
Serial.println(x);
Serial.print("Y = ");
Serial.println(y);
Serial.print("Z = ");
Serial.print(z);
Serial.println("");
delay(250);
}

Simply copy and paste the code in the Arduino IDE, choose the correct port and board and hit upload.

Once the program is uploaded, open the serial monitor. You should see the analogue values in the serial monitor. Now try tilting the accelerometer in different angles. You will see the values change accordingly.

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