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The right sensor to measure acceleration?

Former Member

Hello Everyone and ADVthanksANCE for any input you have.

 

I'm looking for the proper sensor to measure the acceleration of a frisbee. I will be mounting it to the bottom of a frisbee on a PCB I design utilizing most likely an ATMEL AVR microcontroller. I'm in the early design stages so don't have many answers nor are there many requirements decided on. I plan on drilling holes into a frisbee and placing LED's strategically. The LED's I wan't to light up based on the measured acceleration. The faster the frisbee travels or the spin measured, the more lit up it will be. Cost is certainly a consideration since the project is a playtoy and an opportunity to learn from. It won't be marketed nor is it something I plan on showing off to anyone other than my buddy's at night trying to play catch in the dark. I'm trying to figure out the proper sensor to use in this case.

 

Thanks again,

 

Matthew

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    I'd probably stick the main circuit board (the heavy stuff) right in the middle, then put a little accelerometer on the edge. Do consider the weight of the whole thing though, if it's too heavy/not balanced it might not fly well image

     

    Most accelerometers are tiny surface mount components though, are you going to get a PCB made, or is it going to be on perfboard? I would personally suggest designing a PCB on eagle or something and getting it manufactured (not that expensive, depending on where you send it). That way you can use a tiny surface mount accelerometer and make the design as small as possible.

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  • 0

    I'd probably stick the main circuit board (the heavy stuff) right in the middle, then put a little accelerometer on the edge. Do consider the weight of the whole thing though, if it's too heavy/not balanced it might not fly well image

     

    Most accelerometers are tiny surface mount components though, are you going to get a PCB made, or is it going to be on perfboard? I would personally suggest designing a PCB on eagle or something and getting it manufactured (not that expensive, depending on where you send it). That way you can use a tiny surface mount accelerometer and make the design as small as possible.

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  • 0 in reply to Former Member

    Deducing how fast the frisbee is moving across the ground by measuring acceleration will be very difficult becasue the frisbee is spinning and because it experiences a very high acceleration when you throw it followed by decelleration at  amuch lower rate as it travels. This would mean the you would need an accelerometer with a large dynamic range and very good linearity.

    Calculating the angular velocity by measuring the centripetal acceleration with an accelerometer would be much easier. http://en.wikipedia.org/wiki/Centripetal_force

    If you put the accelerometer in right distance from the centre you may be able to make the centripetal acceleration comparable with the linear deceleration of the whole frisbee due to air resistance and then you might be able to separate the two components of acceleration. You would need to use two accelerometers diametrically opposite each other, both would always see the same centripetal acceleration but the linear deceleration would result in a sinusoidal signal (frequency equal to frisbee spin rate,  amplitude proprtional to linear acceeleration or decelleration) superimposed on the steady (ish) centripetal acceleration signal.

     

    You can do some sums based on the Wiki article and perhaps some frisbee tests to work out where to put the accelerometer(s) and the range of accelerations you will see.

     

    Analog devices sell several  suitable surface mount parts. ADXL335 might do you, it's a 3 axis part but you still need two because they need to be in two different places in the frisbee (unless you just estimate angular velocity). You might find the package and operating voltage challenging.

     

    MK