# Using accelerometer sensor to determine speed of person

1. Nov 2, 2004

### cjn200

hello, i'm using an accelerometer (ADXL311) which outputs analog voltage in proportion to g's for X and Y axes. i'm trying to use this to manipulate sound when a person is 'running', basically as speed increases above a certain threshold, but having problems with my formulas for speed.

i've managed to graph these two actions with consistent visual results - it's visually clear when someone is running, etc., but haven't been able to correctly translate this into a usable formula. my known variables are gX, gY, time, and i'm assuming that i'll have to take periodic samples and calculate an average, but so far, i've managed nothing that makes sense.

can anyone help in a language for dummies? i can handle the electronics more or less, but had (embarrassingly enough :uhh:) to look the formula for speed.

thanks!

2. Nov 2, 2004

### Staff: Mentor

I presume that they output an acceleration over their time increment. Acceleration times that time increment is the change in speed over that increment. Add the change in speed over that increment to the starting speed and you have the new speed.

3. Nov 2, 2004

### Integral

Staff Emeritus
Where on the body did you attach the accelerometer. If it is on the feet or legs you will need to do something very different find the velocity of the running person.

4. Sep 27, 2009

### nidhi.monika

Hi everybody,
I desperately need help!!
I am using tri axial accelerometer to calculate speed during sprint. I tried calculating speed and the peak speed from this data is 30m/s (which is not at all possible). I hv data at every .02 secs. I attached the acceleromater on sacrum.

5. Sep 27, 2009

### Integral

Staff Emeritus
You have not given nearly enough information for anyone to help you.

How did you calculate the velocity that you have?

How did you collect and process the data?

6. Sep 28, 2009

### nidhi.monika

hi thanks a tonn for the reply.
I have calculated the speed like this.
Calculation of velocity from discrete acceleration data:

Integral of acceleration will give velocity value. Since data given for acceleration is discrete so we have calculated velocity value at x direction (Vx) through integrating under discrete acceleration data at x direction by using matlab programme. Similarly Vy and Vz was calculated. Total velocity value will be sqrt(Vx*Vx + Vy*Vy + Vz*Vz)
I didnot process data but directly used it (though i saw alot of noise in data but not sure how to process it). could you please tell me about the correct way of collecting data and processing it and the correct procedure of calculating it.
IT will be a great help