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How to decrease fluctuations

Discussion in 'General Electronics Discussion' started by MartinV279, Sep 16, 2014.

  1. MartinV279

    MartinV279

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    1
    Aug 19, 2014
    For a project I've made flex sensors (using piezoresistive material). They pretty much do the job (give about 5 distinct resistance areas for determining position), but the fluctuations in the signal give me a problem. I was thinking of making a filter in the code, but stabilizing them through the hardware would be preferable I think. Any ideas or tips? Generally I don't need the small oscillations, only the greater ones.
    Thanks!
     
  2. Arouse1973

    Arouse1973 Adam

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    1,078
    Dec 18, 2013
    Can you tell us the frequency and amplitude of the oscillations? Better still post an oscilloscope capture here. A circuit diagram would also be good.
    Adam
     
  3. MartinV279

    MartinV279

    14
    1
    Aug 19, 2014
    Thanks for the fast reply. I'm afraid I'll need a day or two to get my hands on the oscilloscope from the lab at uni.
     
  4. Arouse1973

    Arouse1973 Adam

    5,164
    1,078
    Dec 18, 2013
    That's fine, it's better we see what going on. In the meantime maybe you can explain a bit more about the project and how it's designed to work and what it's for.
    Adam
     
  5. MartinV279

    MartinV279

    14
    1
    Aug 19, 2014
    I'm making a sign language glove and due to budget deficit I'm using homemade sensors. They are made with velostat material from black conductive tapes. Due to imperfection because it's all hand made/cut/taped it's kind of unstable. So I'm trying to stabilize the signal with hardware. The alternative is to filter out all changes below 2% in the code, but I'm not a fan of software solutions if there's a hardware solution. I was thinking of a low pass filter (100nF capacitor) and then subtract the output of the filter from the output of the sensor.
    The sensor give resistances in the range of 15kΩ-60kΩ. The nominal value is about 27kΩ.
     
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