An accelerometer is a device that measures proper acceleration, i.e the acceleration (or rate of change of velocity) of a body in its own instantaneous rest frame. For example, an accelerometer at rest will measure an acceleration due to Earth’s gravity, straight upwards (by definition) of g ≈ 9.81 m/s2. By contrast, accelerometers in free fall (falling toward the center of the Earth at a rate of about 9.81 m/s2) will measure zero.
-
object at rest
-
falling object
The first usage or application of accelerometer in consumer electronics was popularized by Steve Jobs in Apple iPhone. Accelerometers have multiple applications in industry and science. Highly sensitive accelerometers are components of inertial navigation systems for aircraft and missiles.
The ADXL34 accelerometer is a multi-axis accelerometer:
Single- and multi-axis models of accelerometer are available to detect magnitude and direction of the proper acceleration, as a vector quantity, and can be used to sense orientation (because direction of weight changes), coordinate acceleration, vibration, shock, and falling in a resistive medium (a case where the proper acceleration changes, since it starts at zero, then increases). Micromachined microelectromechanical systems (MEMS) accelerometers are increasingly present in portable electronic devices and video game controllers, to detect the position of the device or provide for game input.
Connection to Raspberry Pi
-
Connections
-
GND –> GND
-
3V –> 3V3
-
SDA –> SDA
-
SCL –> SCL
ADXL supports both I2C and SPI connections
I use i2C
Here are the steps:
-
- Add I2C to the pi config
sudo nano /etc/modules
- Add I2C to the pi config
and add the followign line:
i2c-bcm2708
i2c-dev
-
2 Reboot
sudo reboot -
- Install smbus
sudo apt-get install python-smbus i2c-tools git-core
- Install smbus
*4. Test ADXL345 is found on the i2c bus:
sudo i2cdetected -y 1
You should see a device at address 53.
-
- Clone the repo: `https://github.com/pimoroni/adxl345-python