Connect an Accelerometer to a Raspberry Pi


Tag: Project

Accelerometers measure the acceleration in their own rest frame by measuring the movement of a damped mass. During acceleration the mass will move in the opposite direction until the force of the damping mechanism (such as a spring) equals the force of acceleration. The damping force can then be measured to provide a value for the accelerating force.

As Earth's gravity results in a constant upwards acceleration for any body at rest on its surface, accelerometers can be used to determine orientation. This property could be very useful for a navigation system in a Raspberry Pi based robot. The following tutorial will demonstrate how an Accelerometer can be hooked up to a Pi and how the data can be visualised.

Equipment required

  • 5 male to female wires
  • Male headers
  • Breadboard
  • Soldering iron
  • Adafruit LIS3DH

Pi Setup

  • Make sure the I2C communication protocol is activated on the pi
sudo raspi-config
  • Under 5. Interfacing Options make sure I2C is enabled
  • Make sure the correct modules are included in the module file /etc/modules, it should contain the lines:
i2c-bcm2708
i2c-dev
  • Restart the Pi

Connections

An image of connections between the accelerometer and the Pi can be found here.

  • Connect Vin to the 3v3 pin (pin 1)
  • Connect Gnd to any ground pin (pin 6)
  • Connect SCL to the I2C clock (pin 5)
  • Connect SDA to the I2C data (pin 3)
  • Connect INT to any free digital IO pin (pin 31)

Testing the connection

  • Install the libraries required to talk to I2C devices
sudo apt-get install i2c-tools python-smbus
  • Look at the connected I2C devices
sudo i2cdetect -y 1
  • The device should appear in the 0x18 address.

Visualising acceleration and rotation

  • In your python virtual environment install the required modules
pip3 install adafruit-circuitpython-busdevice
pip3 install adafruit-circuitpython-lis3dh
  • Write a python script to visualise the acceleration and rotation.
  • Run them to see the accelerometer in action.
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