Tilt sensor (Part 1)

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Accelerometers are among the sensors that have experienced the greatest development in the ten past years. From automotive to gaming applications not talking about phones, they are included in many equipements. As a consequence of this massive use, their price is falling down to acceptable prices for the hobbyst! The choice of an accelerometer depends on multiples factors:

  • Number of axis (from 1 to 3, in one package)
  • Dynamic range
  • Sensitivity
  • Output (analog or digital)
  • Footprint

The one I decided to start with comes Adafruit Industries. It uses a Analog Device chip which is mounted on a small PCB.

The ADXL335 is a small, low power, 3-Axis ±3 g accelerometer. The ADXL335 must be fed with a single-supply ranging from 1.8 V to 3.6 V and typically draws less that 0.5 mA. To each axis corresponds an analog output line. The signal is ratiometric and must be filtered according to the sampling requirement.

The signal is proportional to the acceleration along each axis as per the following diagrams:

Note that at rest, the Z axis reading shows 1 g which is the result of the measurement of the gravitational force. This shall be extremly usefull for tilt sensing…

Note: For basic tilt sensing use mechanical devices such as the one available from AdaFruit Industries. Accelerometer based tilt sensor are able to provide pitch and roll information expressed in angular values.

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