 In previous work, a 3D compass was constructed using two separate 2-axis magnetometer modules and a 2-axis accelerometer. The accelerometer allows us to compensate for variations in pitch and roll and deliver a reliable heading. The 3D compass module combines a 3-axis magnetometer and a 2-axis accelerometer into a single board. The device connects to the 8-wire bus and includes both TTL-level and RS-232 level communication capabilities. Raw sensor values are transmitted to the host computer which can then calculate the magnetic heading.  The 3D compass has been used in a variety of applications including directional soundscapes and the Curator’s Wand. Another area of interest involved embedding the compass in a foam football. The raw magnetometer readings were streamed via Bluetooth to a host PC. As the ball rolls along a floor, the magnetic field vector traces a circle in the compass’s coordinate system. The properties of this circle can be used to derive the direction and speed of rotation of the ball which can then be fed into dead-reckoning systems to give an estimate of position information. |