DIGIKEY DKSB1002A3-axis accelerometer

Arduino Unomicrocontroller board

Parallax USB Oscilloscopemeasure voltage vs. time

Acquiring Data from Accelerometers

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http://www.analog.com/static/imported-files/data_sheets/ADXL335.pdf

data sheet for accelerometer is available at . . .

• 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

• COM - ground• VSS - power (we will provide 5V)• X - acceleration in x-direction• Y - acceleration in y-

direction• Z - acceleration in z-direction

Implementing a 3-axis Accelerometer: Hardware

xy

z

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COM - groundVSS - power (we will provide 5V)X - acceleration in x-directionY - acceleration in y-directionZ - acceleration in z-direction

Implementing a 3-axis Accelerometer: Wiring to Arduino

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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);}

Implementing a 3-axis Accelerometer: Programming

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Implementing a 3-axis Accelerometer: Analysis of Output

• 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: _________

xy

z

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Implementing a 3-axis Accelerometer: Angle Measurement

xy

z

1g (perceived vertical acceleration)

ax

x

x

+x

θx = asin(ax/g)

• 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? ___________

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Measuring Output of Accelerometer with Parallax Scope

• 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 10k

5V

switch

trigger input