By measuring the amount of acceleration due to gravity, an accelerometer can figure out the angle it is tilted at with respect to the earth. By sensing the amount of dynamic acceleration, the accelerometer can find out how fast and in what direction the device is moving. Using these two properties, you can make all sorts of cool projects, from musical instruments (imagine playing and having the tilt connected to the distortion level or the pitch-bend) to a velocity monitor on your car (or your children's car). This 3-Axis Accelerometer is reborn with a sweet new chip and great new price.

The 3-axis accelerometer module carries an MMA7361 chip from Freescale. The MMA7361 operates in 2 selectable sensitivity modes, +/- 1.5g, and 6g. The sensor board defaults to 1.5g. Add the shunt or use the GS pin for software selection of 6g sensitivity.

The 3-Axis Accelerometer sensor will operate between 2.2 and 6 volts. Because the MMA7361 chip only will deal with 3.6 volts maximum,  the sensor is equipped with a low-dropout regulator so the sensor will work, out of the box with an Arduino or other 5 volt microcontroller. At 5 volts the sensor draws around 50 uA with the shunt off and 100 uA with the shunt on. The current draw at 3.3 V is 150 / 200 uA respectively.

The 3-axis accelerometer module comes as a kit with a 5-pin male headers, a two pin header, and a shunt for G selection. The sensor defaults to 1.5G so you don't have to install the two pin header if you are only using the more sensitive setting.

Applications

• Laptop PC: Freefall Detection
• Cell Phone: Image Stability, Text Scrolling, Motion Dialing, E-Compass
• Pedometer: Motion Sensing
• Portable Handheld: Text Scrolling
• Navigation and Dead Reckoning: E-Compass Tilt Compensation
• Gaming: Tilt and Motion Sensing, Event Recorder
• Robotics: Motion Sensing

Specifications

• Built-in 5V tolerance protection
• Selectable Sensitivity (1.5g/6g)
• Low Current Consumption: 500 μA
• Sleep Mode: 3 μA
• Low Voltage Operation: 2.2 V – 3.6 V
• High Sensitivity (800 mV/g @ 1.5g)
  
• Dimensions: .950" x .550" x .105" (thick) with no headers

Resources

• MMA7361 Datasheet
• 3 Axis Accelerometer Schematic
• Tilt Sensing with the Accelerometer Arduino Sketch - illustrates using trig to get headings.