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living with the lab
Acquiring Data from Accelerometers
DIGIKEY DKSB1002A
3-axis accelerometer
Arduino Uno
microcontroller board
Parallax USB Oscilloscope
measure voltage vs. time
data sheet for accelerometer is available at . . .
http://www.analog.com/static/imported-files/data_sheets/ADXL335.pdf
living with the lab
Implementing a 3-axis Accelerometer: Hardware
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DKSB1002A is a prototyping board
$20 from www.digikey.com
Screw holes for mounting board onto “object of interest”
Board is ~ 20mm square
ADXL3355 3-axis accelerometer chip
• 3-axis
• ±3g
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z
x
y
COM - ground
VSS - power (we will provide 5V)
X
- acceleration in x-direction
Y
- acceleration in y-direction
Z
- acceleration in z-direction
living with the lab
Implementing a 3-axis Accelerometer: Wiring to Arduino
COM - ground
VSS - power (we will provide 5V)
X
- acceleration in x-direction
Y
- acceleration in y-direction
Z
- acceleration in z-direction
living with the lab
Implementing a 3-axis Accelerometer: Programming
void setup()
{
Serial.begin(9600);
}
void loop()
{
int xaccel = analogRead(0);
int yaccel = analogRead(1);
int zaccel = analogRead(2);
Serial.print(xaccel);
Serial.print(" ");
Serial.print(yaccel);
Serial.print(" ");
Serial.println(zaccel);
}
living with the lab
Implementing a 3-axis Accelerometer: Analysis of Output
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Output from accelerometer will vary from 0 to 5 V
Output when +x points upward:
__________
Output when +x points downward: __________
Difference: _______
Change in acceleration = 2g
Change in accelerometer per g: ___________
Output when accelerometer is flat: _________
z
x
y
living with the lab
Implementing a 3-axis Accelerometer: Angle Measurement
+x
qx
ax
θx = asin(ax/g)
qx
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z
x
y
1g (perceived vertical acceleration)
Expected output of Arduino when accelerometer is flat: _________
Expected output of Arduino when accelerometer is at 45 degrees? ________
If the Arduino output is 350, then what is the angle? ___________
living with the lab
Measuring Output of Accelerometer with Parallax Scope
5V
switch
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Attach channel 1 leads between x-acceleration signal and ground
Oscilloscope plots voltage vs. time
Export data to a file to acquire voltage (or acceleration) vs. time data
Example of how a switch circuit is used to trigger data acquisition
trigger input
10kW