Wireless Tilt Sensing in an O.T. Application

by Pinky Magbanua

The WiTilt v2.5 is a 2.4GHz Wireless 3-axis Tilt Sensor from Sparkfun. It employs a FreeScale MMA7260Q triple-axis accelerometer and a class 1 Bluetooth link from BlueRadios.

MMA7260Q datasheet

BlueTooth Module DIP datasheet

The Triple Axis Accelerometer

Here is a link to Tom Igoe's original sensor report summary.

This is a surface mount integrated circuit accelerometer that runs on low voltage (2.2V - 3.6V). It measures a change in capacitance through 2 g-cell beams that serve as back to back capacitors reacting to a movable beam located in between them. The illustration below demonstrates this mechanism.

This change in capacitance is then converted into voltage outputs which reflect movement changes along the X, Y, Z axes. This accelerometer also features a 4-level sensitivity scale (1.5g, 2g, 4g, 6g), with 1.5g setting being the most sensitive. It measures both (+) and (-) acceleration. It has 16 pins, only 8 of which are connected with functions.