How to use an accerlometer to trun on an led

Other Hardware Sensors
1

i am working on a project where i have an adxl 377 accelerometer hooked up to the arduino and i want to use the analog output from the accelerometer to turn on the led. i want a threshold 70g but to start off i just need to know how i should go about writing the code to turn the led on. i tried to write the code but its not working. any help would be appreciated. I have included the code below

// these constants describe the pins. They won't change:
const int xpin = A3; // x-axis of the accelerometer
const int ypin = A2; // y-axis
const int zpin = A1; // z-axis (only on 3-axis models)
int led = 13;

void setup()
{
// initialize the serial communications:

Serial.begin(9600);
pinMode(led, OUTPUT);
}

void loop()
{

int X = analogRead(xpin);
int Y = analogRead(ypin);
int Z = analogRead(zpin);

float Volt_X = X * 0.003222656;
float Volt_Y = Y * 0.003222656;
float Volt_Z = Z * 0.003222656;

float Cal_X = (Volt_X - 1.65)*1000.0;
float Cal_Y = (Volt_Y - 1.65)*1000.0;
float Cal_Z = (Volt_Z - 1.65)*1000.0;

float G_X = (Cal_X/6.5)-1.49;
float G_Y = (Cal_Y/6.5);
float G_Z = (Cal_Z/6.5);

// float Total_Gs = sqrt(sqrt(G_X)+ sqrt(G_Y) + sqrt(G_Z));

Serial.print("X_Value");
Serial.print(G_X);
Serial.print("\t");
Serial.print("Y_Value");
Serial.print(G_Y);
Serial.print("\t");
Serial.print("Z_Value");
Serial.print(G_Z);
Serial.print("\t");

if (G_X == 70)
{
digitalWrite(led,HIGH);
delay(1000);
}

Serial.println ();

delay(100);

}

2

Hi,

I know nothing about the accelerometer side of things so I'll assume you have that mastered :stuck_out_tongue:

Seems the problem part is this? (Note the use of code tags: the # above the :wink: smily)

 if (G_X == 70)
  {
    digitalWrite(led,HIGH);
    delay(1000);
  }

First you should probably be looking for greater than or equal to: your equals to will seldom be exactly matched. Then I guess you need to switch it off next time round if it's less than 70? So try something like this:

 if (G_X >= 70)    //note >= now
  {
    digitalWrite(led,HIGH);
    delay(1000);
  }
else
  {
    digitalWrite(led,LOW);  // turn off if G_X is not >= 70
  }

That should get you started.

You eventually might like to look at BlinkWithoutDelay so as not to tie your processor up just so the light can be seen....

3

will the device actual report a 70g value ?

And do you realise, you are only looking at the x direction ?

4

For what particular reason are you subtracting 1.49 when you calculate G_X ?