1. Acquiring Data from an ADXL335 Accelerometer
DIGIKEY DKSB1002A Evaluation Board
3-axis accelerometer
Arduino Uno
microcontroller board

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3. Implementing a 3-axis Accelerometer: Wiring to Arduino
COM
Ground
VSS
Power (5V) X
Acceleration in x-direction Y
Acceleration in y-direction Z
Acceleration in z-direction

4. Programming associates a time with each set of accelerations
void setup() {
Serial.begin(9600); }
void loop()
int xaccel = analogRead(0);
int yaccel = analogRead(1);
int zaccel = analogRead(2);
unsigned long timevar = millis();
Serial.print(timevar);
Serial.print(" "); Serial.print(xaccel);
Serial.print(" ");
Serial.print(yaccel);
Serial.println(zaccel);
associates a time with
each set of accelerations

5. Calibration Output when +x points upward: xaccel=627
Output when +x points downward: xaccel=401
Difference = 627 – 401 = 226
Change in acceleration = 2g
Change in accelerometer per g: 𝑔 = 113 𝑔
Output when accelerometer is flat: 627 – 113 = 514 x y z

6. Angle Measurement z x y θx = asin(ax/g)
1g (perceived vertical acceleration) ax qx +x
θx = asin(ax/g)
Angle Measurement x y z
The Arduino will output 514 when the accelerometer is flat; the output changes by 113 per “g”
Expected output of Arduino when accelerometer is at 45 degrees?
𝑎 𝑥 = sin 45 ∙𝑔=0.707𝑔
𝑜𝑢𝑡𝑝𝑢𝑡= 𝑔∙ 113 𝑔 =594
If the Arduino output is 450, then what is the angle?
𝑎 𝑥 = 450− 𝑔 =−0.57𝑔 𝑎𝑛𝑑 𝜃 𝑥 = asin −0.57𝑔 𝑔 = −34.5 °
Don’t forget that the accelerometer can also measure actual acceleration (not just angles)

7. Example Application
The piezospeaker below outputs a frequency that varies with the acceleration in the x-direction. The equation for computing the frequency is chosen so that the device makes an audible noise that varies when rotating or shaking the device.
void setup(){Serial.begin(9600); }
void loop() {
int xaccel = analogRead(0);
int freq = 1500+xaccel*2;
tone(7,freq);
Serial.print(xaccel);
Serial.print(" ");
Serial.println(freq); }