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Pressure sensitive surface

Discussion in 'Sensors and Actuators' started by darren adcock, Dec 13, 2017.

  1. darren adcock

    darren adcock

    462
    34
    Sep 26, 2016
    Hi folks


    I would like to control the CV controls on my synthesizer with pressure. I have been through piezo discs and soft pots but neither have done what i would like.

    I would like to apply pressure to any part of a given surface (hence softpots didn't do the job, unless i've missed out on a type).

    My main problem is that i can't find a way to say apply a certain pressure and sustain a signal to hold for example a certain frequency of an oscillator. The piezo discs can do this, but they are mighty picky/sensitive... maybe i need to condition the signal more... or the envelope of the signal....

    Anyhow, i'm researching away but have kinda ran into a dead end so i thought i'd ask here and see what i've missed

    thanks in advance

    Darren
     
  2. darren adcock

    darren adcock

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    34
    Sep 26, 2016
    http://www.nakka-rocketry.net/loadcell/amp_circ2a.gif

    Looking further i have come across Load cells and wheatstone bridges.. as an analogue front end to a larger circuit which requires a digital section also...I'd prefer to keep it all analogue if possible.... but will keep looking.
     
    Last edited: Dec 14, 2017
  3. darren adcock

    darren adcock

    462
    34
    Sep 26, 2016
    Oh and i realise I've not said how much weight, in terms of what the load might be. It's for a project where by a person can draw onto a surface. It's part of research into developing therapeutic tools. So in this case it would combine Drawing and sound.
     
  4. kellys_eye

    kellys_eye

    4,281
    1,144
    Jun 25, 2010
    There are digitising pads that have pressure sensitive pens for drawing purposes.

    Monitoring the pressure on a pen tip seems reasonably achievable (ferrite core moving in/out a coil to alter inductance/frequency).
     
  5. darren adcock

    darren adcock

    462
    34
    Sep 26, 2016
    Thanks K.E.

    I will look into this now...

    putting the sensor inside the drawing implement is an approach I'd not considered.
     
  6. darren adcock

    darren adcock

    462
    34
    Sep 26, 2016
    I guess also if after researching ferrite core and coil approach there'd be no reason for this to not be part of a surface
     
  7. darren adcock

    darren adcock

    462
    34
    Sep 26, 2016
    pressure sensor.gif Pretty much solved the initial problem with two copper strips a piece of conductive foam and part of a circuit i took from a Thomas henry book. I'm not quite sure how the initial variable voltage part of the circuit works. Apart from the foam increases in conductivity as it is compressed. I can draw very lightly on this surface and get a lot of modulation for my synths inputs.

    I hope this next bit makes sense.

    I would like to sample the voltage at timed events. So i could have two outputs one running in real time and one sampling the voltage at specific times. In my head it would be sort of a delay type effect? I'm probably trying to reinvent the wheel here, so just let me know if so and i'll go off and read what's suggested.

    Thanks in advance

    Darren
     
  8. darren adcock

    darren adcock

    462
    34
    Sep 26, 2016
    No worries now, Yup, defo reinventing the wheel. Sample and Hold... now i know what this means and how to use it.
     
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