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 The ANALOG DEVICES ADXL202 accelerometer sensor can easily be interfaced to a microcontroller, in this instance a Microchip PIC16F84A microcontroller. A single ADXL202 accelerometer is able to sense the Pitch and Roll experienced by a stationary or moving platform.
The ADXL202 outputs are Duty Cycle Modulated (DCM) signals, whose duty cycles (ratio of pulsewidth to period) are proportional to the acceleration in each of the two sensitive axes(pitch and roll). The outputs may be measured directly with a microcontroller counter requiring no A/D converter. The DCM period is adjustable from 0.5mS to 10mS via a single resistor (RSET). If an analog output is desired , an analog output proportional to the acceleration is available from the ‘XFILT’ and ‘YFILT’ pins, or may be reconstructed by filtering the duty cycle outputs. When the tilt angle is varied along the sensitive ‘X’ and ‘Y’ axis the Accelerometer vector changes and the ADXL202 responds by changing the PWM duty cycle output. As the horizontal plane of the project board is altered, by physically moving it, the accelerometer PWM duty cycle changes accordingly, the program converts the PWM data to digital data and then displays it on the LCD, giving a visual indications of the programs performance. Accelerometers have many applications, a feature of interest being the orientation control of Quadcopters and similiar flying vehicles.
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