What is Degrees Of Freedom, 6DOF, 9DOF, 10DOF, 11DOF

"Degrees Of Freedom" or "DOF" is a number of axis and sensors combined for balancing a plane, a helicopter or a robot.

  • 3DOF : This could be a 3-axis accelerometer or it could be a 3-axis gyroscope.
  • 6DOF : This is mostly a 3-axis accelerometer combined with a 3-axis gyroscope.
    Examples:
    • To control a remote control (RC) plane or helicopter or a self-balancing robot, both the information of the accelerometer and gyro are needed.
    • An other example of 6DOF is a combination of an accelerometer and a magnetometer for a tilt-compensated compass.
    • Many game controllers, phones and tablets contain a 6DOF sensor for motion information.
  • 9DOF : This is mostly a 6DOF, combined with a magnetometer (compass).
  • 10DOF : This could be a 9DOF, combined with a baromic pressure sensor. The baromic (or absolute pressure) sensor can be used as an indication for the height.
  • 11DOF : This could be the 10DOF, combined with a GPS module.

Multiple sensors in a chip or on a board.

A 9DOF module for example, could be a circuit board with three sensors. But some chips have a accelerometer and a gyro inside. In that case, only that sensor and a magnetometer is needed.

Interface with the Arduino

Some sensors have analog outputs, and can be easily connected to an Arduino. The software reads the analog signal with a single function: "analogRead()". Most Arduino's have only 6 analog inputs (the Arduino Mega has 16 analog inputs) so a 6DOF sensor can be connected without extra hardware to most Arduino boards.

Most sensors have an I2C or SPI interface. The analog-to-digital-conversion (ADC) is done inside the sensor. That increases the accuracy. Some sensors use 16-bits which is more than the 10-bits of the Arduino. Some sensor are very complicated and can be programmed with firmware.

To interface the Arduino with 6DOF, 9DOF, 10DOF, 11DOF sensors, see: http://playground.arduino.cc/Main/InterfacingWithHardware#DOF

Interesting links:

Wikipedia about Degrees Of Freedom: http://en.wikipedia.org/wiki/Degrees_of_freedom_%28mechanics%29

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