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Memsic 2125 — Parallax Forums

Memsic 2125

EMPTY_CEMPTY_C Posts: 29
edited 2009-08-13 03:29 in Accessories
I have been playing with the Memsic 2125 and was hoping i could integrate it into my RC car. I wish to calculate the acceleration of the car laterally and radially.· I think that there is an issue with getting an accurate signal.· If the car is accelerating and going up an incline doesn't that interfere with the actual "G" calculation? I have the accelerometer on my desk the forces seem to bounce around a lot and the board isn't even moving. I was thinking about using a low pass filter to reduce the noise. But if this board were on a slight incline is it true that it will give unreliable "G Force" results?

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Comments

  • John AbshierJohn Abshier Posts: 1,116
    edited 2009-08-12 16:41
    A accelerometer by itself cannot distinguish between the car's acceleration and the acceleration due to gravity or going up/down an incline.

    John Abshier
  • kwinnkwinn Posts: 8,697
    edited 2009-08-12 16:50
    Depends on what you mean by "unreliable G force results". If the car is going up an incline it is reading the sum of the force from acceleration and the force of gravity acting on it. This is the actual force acting on the car, so in that sense it is quite reliable. If you are using the reading to calculate the change in speed of the car however, it would give an incorrect result since you have not taken the force resulting from being on an incline into account. The same would be true for lateral forces.

    To correct for the tilt caused by being on an incline would require a sensor that measures tilt without being affected by acceleration forces, and I am not aware of any such sensors.
  • EMPTY_CEMPTY_C Posts: 29
    edited 2009-08-12 21:30
    so if i take the resolved acceleration and the angle of the vehicle i could find the acceleration of the RC car?
  • Jessica UelmenJessica Uelmen Posts: 490
    edited 2009-08-12 23:28
    Hi EMPTY_C,

    Take a look at Chapter 6, Activity #5 in Smart Sensors and Applications. It demonstrates how to datalog the acceleration forces on an RC car using the MX2125.

    Hope this helps!

    Jessica

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    Jessica Uelmen
    Education Department
    Parallax, Inc.
  • kwinnkwinn Posts: 8,697
    edited 2009-08-13 03:29
    re > so if i take the resolved acceleration and the angle of the vehicle i could find the acceleration of the RC car?

    Yes. The trick is finding a way to accurately measure the angle of the vehicle while it is accelerating.
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