How to calculate velocity from accelerometer (LSM303DLM) !!!!

Other Hardware Sensors
1

I have an accelerometer (LSM303DLM) and with Arduino UNO i want to find velocity

i try this formula : Vf = Vi + a*t , but i found that my velocity it affected by acceleration angle ,and the other problem is my acceleration is very sensitive and affected my velocity ...

if i used gyroscope with combination the accelerometer i will take corrected velocity values ?

2

How are you getting your values?
What are you using for time?

That formula is for "final velocity" after a certain amount of time. Is that what you want?
Or instantaneous velocity (right now)?

What is "it" giving you?

Code?

3

i am getting the acceleration values from accelerometer. The time that i used is the same of the delay time t = 0.02 ... is correct ??
is verry sensitive the LSM303DLM and the values change very easy.... i think it happened from angle velocity...my project is to do balck box from car
which is calculate the velocity . from this equation i take the final velocity but i am ton sure

my code is :

// velocity_i is the velocity initial
//acc1122.y is my accelaration
// 0.2 is the time

distance = (velocity_i * 0.2) + (0.5 * acc1122.y * 0.2*0.2);
velocity_f = ((2 *distance)/0.2) - velocity_i ;

velocity_f = abs (velocity_f);
distance = distance /(10 *10);

// velocity_i = velocity_f ;

velocity_i = velocity_f - acc1122.y * 0.2 ;
Serial.print("Velocity: ");
Serial.println ( velocity_f);