Accelerometers

Types:

• Single-, dual-, or triple-axis
• Analog or digital output
• Dynamic and/or static (tilt) measurements

Theory of Operation (ADXL family and others):

• Micro-machines mass-spring system on top of silicon wafer

• Acceleration is proportional to displacement of the mass: a = k x / m
• Uses differential capacitor setup, which is proportional to x for small displacements

Analog Devices ADXL203: dual-axis, voltage output

• Tilt sensing:

• The internal update rate of the accelerometer can be adjusted in the range 0.5 Hz to 2.5 kHz using capacitors (C_x, C_y).

Interfacing the ADXL203 to the Arduino:

• Connect X_out and Y_out directly to any analog input pins of the Arduino.

• Use the analogRead( pin ) function to directly measure the resulting voltage output from a given axis.

• The same example sketch used to measure variable resistances can be used for this purpose.

Interfacing the Arduino to other Accelerometers:

• Parallax Memsic 2125 Dual-Axis Accelerometer
• LIS302DL Triple Axis Accelerometer, Arduino program, SCL to Analog Pin 5, MOS1 to Analog Pin 4, Vcc to 5V, Gnd to Gnd.
• MMA7260Q Triple Axis Accelerometer, read variable output voltage from X, Y, or Z pins into any analog pin, Vcc to 3.3V, GS1 and GS2 to Gnd (for 1.5g), SLP to 3.3V.