Acquiring data from accelerometers and photoresistors
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MEEN 486. Acquiring Data from Accelerometers and Photoresistors. Arduino Uno microcontroller board. DIGIKEY DKSB1002A 3-axis accelerometer. Parallax USB Oscilloscope m easure voltage vs. time. EXTECH Light Meter calibrate the photoresistor. Photoresistor

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Acquiring Data from Accelerometers and Photoresistors

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Acquiring data from accelerometers and photoresistors

MEEN 486

Acquiring Data from Accelerometers and Photoresistors

Arduino Uno

microcontroller board

DIGIKEY DKSB1002A

3-axis accelerometer

Parallax USB Oscilloscope

measure voltage vs. time

EXTECH Light Meter

calibrate the photoresistor

Photoresistor

resistance changes with light level


Acquiring data from accelerometers and photoresistors

MEEN 486

Implementing a 3-axis Accelerometer: Hardware

  • 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

z

x

y


Acquiring data from accelerometers and photoresistors

MEEN 486

MEEN 486

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


Acquiring data from accelerometers and photoresistors

MEEN 486

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);

}


Acquiring data from accelerometers and photoresistors

MEEN 486

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: _________

z

x

y


Acquiring data from accelerometers and photoresistors

+x

qx

ax

qx

1g (perceived vertical acceleration)

MEEN 486

Implementing a 3-axis Accelerometer: Angle Measurement

z

x

y

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? ___________


Acquiring data from accelerometers and photoresistors

MEEN 486

Measuring Output of Accelerometer with Parallax Scope

5V

switch

trigger input

10kW

  • 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

  • Using a switch circuit to trigger data acquisition


Acquiring data from accelerometers and photoresistors

MEEN 486

Calibrating a Photoresistor

  • Build photoresistor circuit

  • Connect the analog output of the circuit to an oscilloscope, Arduino or other data acquisition device

  • Associate output of the photoresistor circuit as measured by your data acquisition device with the light reading from a calibrated light meter

  • Use linear regression to determine an equation that relates the output of your data acquisition device to light level

5V

photoresistor

analog pin 3

10kW


Acquiring data from accelerometers and photoresistors

MEEN 486

Extension to Other Sensors

  • This presentation shows how an accelerometer and a photoresistor can be used to record physical measurements

  • An Arduino or a Parallax Oscilloscope, two inexpensive devices, were used to acquire data

  • You can check out any of the items discussed in this presentation for your MEEN 486 project; refer to the equipment link on the MEEN 486 website for other equipment and devices that are available to you

  • The principles applied here can be extended to other sensors that output a voltage signal


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