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Discussion in 'General Electronics Discussion' started by wdmccall18, Sep 8, 2010.

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  1. wdmccall18

    wdmccall18

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    Sep 8, 2010
    I'm looking for a device or maybe just a direction on this problem. I need some sort of vibration sensor what will digitally display the number of times a vibration occurs. I don't need to know anything about the vibration just the number of times a vibration occurs. Like a digitally displayed numeric counter. If anyone has any idea of a product, part, system etc that sounds like this PLEASE let me know! Thanks for your time!
     
  2. KMoffett

    KMoffett

    719
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    Jan 21, 2009
    What frequency and amplitude of vibrations do you want to count?...1 bump per hour?...3600rpm?...??? You need a lot more details. How about describing the whole project.

    Ken
     
  3. NickS

    NickS

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    Apr 6, 2010
    I recently finished up a start up circuit based on vibration. Specifically the device was to wake up when bumped or picked up. So the vib frequency was very very low and I was only interested in a discrete input. What I used was a piezo film vibration sensor with attached mass(the mass is a weight added to the end of the film that reduces the frequency response). Next I just listened for a rising edge from the sensor and ignored the the rest for a small time(because the sensor output will oscillate with the film as it slows to a stop)

    But I think you could easily design a circuit that wold filter the output and trigger a digital counter. Now what to do about reading out the result depends on your needs. It could be as simple as lighting up a LED array to give you binary view of an 8 bit word. Or as fancy as a uC counting the shocks and displaying the count on an LCD display.

    -Nick-

    But I am not aware of any off the shelf already made solutions for this. I would not be suprised to lean they exist but I will let you google that.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
    2,779
    Jan 21, 2010
    Long, long ago I worked in a mining company. One of the tasks some of my colleagues had was to place data-loggers on conveyer motors. They were logging vibrations and using this to determine is there were problems with bearings, gearboxes, etc.

    The point of this is that I can't remember exactly what the sensors were called. If I could I would Google them and then give you a link.

    At present the best I can do is look a bit stupid...

    OK, the best I can come up with is this.

    Normally the vibration is not just a simple count as a single event typically generates a series of vibrations that decay over a period of time.

    If you imagine a motor with an unbalanced rotating element, there will be an oscillation defined by the rotational speed, as well as others caused by the resonant frequency of the supporting structure (which hopefully will be very different)

    So what is it *exactly* that you're trying to measure (or count)?
     
  5. Militoy

    Militoy

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    Aug 24, 2010
    The types I use most often are accelerometers and microphones - coupled through an instrument amplifier to a scope or spectrum analyzer. Depends on whether you are measuring structure-borne or airborne vibration. You need to pick the sensitivity and resolution of the instruments to match the level of vibration expected, and the data needed. It sounds to me like you need only very basic data - like from a contact guitar microphone and low-power amplifier connected to a freq counter.
     
  6. wdmccall18

    wdmccall18

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    0
    Sep 8, 2010
    Ok, here is my situation. I'm in the beginning stages of this project in which I'm trying to assemble a device that will attach to the end of a baseball bat and receive vibrations that will digitally display the number of times a ball has been struck.

    -"For most single walled aluminum bats this mode has a frequency around 2000Hz; for most double walled aluminum bats it is around 1500Hz; and for some recent composite bats it is as low as 1000Hz. This vibrational shape radiates sound in a quadrupole pattern - quadrupoles are rather inefficient sound radiators, but the frequency (2000Hz) is in the range of sounds most readily heard by the human ear so the "ping" can sound quite loud".

    *Youth bats may have a little higher freq because the diameter is almost the same as a adult bat but has a shorter bat length.

    -thanks for the link steve
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
    2,779
    Jan 21, 2010
    Personally, I don't think you will have to worry about the frequency. If you hit a ball, you'll get a significant signal.

    Maybe you'll have to further categorise that signal if you want to be able to discriminate between say hitting a ball and dropping the bat, or tapping it on the ground.
     
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