Accelerometer : Motion : Minimum Threshold

JpEncausse · September 2015

Hi,

I try to log the motion of a door on mma8452qModule.

mma8452qModule.configureMotionDetection().setThreshold(threashold).setAxes(Mma8452qAccelerometer.Axis.values()).commit();

For objects, threshold 1.1 is a good value but on doors slowly opened I can't detect motion (I know I should have a gyroscope) If I set a threshol of 0.8 the motion is always detected is it normal ? When I display live axis motion is well displayed under 1.0

An other question: with previous code can I have access to the acceleration: sqrt(x² + y² + z²) or do I have to do axis sample ?

Thanks

Eric · September 2015

I'll get back to you on the motion question, i have not had a chance to think about motion detection on the door motion.

You can only retrieve the magnitude of the acceleration vector from the axis sampling.

JpEncausse · September 2015

Thanks,

I know that sen.se use gyroscope to detect motion on "axis" : doors or drawer. So I'll try whe Kickstarter Metaware C.

But yes I was surprised that at < 1.0f the motion was always triggered

Eric · September 2015

The MMA8452Q chip reports active movement when the device exceeds a certain accelereation which can be caused by a sudden jerk or even tilting the sensor. You can try configuring the duration (debounce) parameter in the MovementConfigEditor interface to see if it improves the movement detection.

Free Scale also provides some application notes on the motion/free fall detection which you may find helpful:

http://cache.freescale.com/files/sensors/doc/app_note/AN4070.pdf?fpsp=1&WT_TYPE=Application%20Notes&WT_VENDOR=FREESCALE&WT_FILE_FORMAT=pdf&WT_ASSET=Documentation&fileExt=.pdf

Accelerometer : Motion : Minimum Threshold

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