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Resistive touch screen film as sensor.

Discussion in 'Sensors and Actuators' started by matmat9090, Oct 18, 2018.

  1. matmat9090

    matmat9090

    4
    0
    Oct 18, 2018
    Hello i was wondering about the characteristics of resistive touch screen or digitizer film like the one in this link

    https://www.ebay.co.uk/itm/12-1-5wi...h=item44217c5d90:g:B8sAAOSwKMxbMxBy:rk:1:pf:0

    I'm not intending to use this as a touch screen digitizer.
    I was hoping to use it as a sensor to detect the amount of film there is an object on. Would the total resistance between some of the output wires decrease the larger the area of film pressed down was.

    if anyone has any useful links to data sheets or similar questions that would be most appreciated.
    thanks in advance.
     
  2. Externet

    Externet

    632
    131
    Aug 24, 2009
    From what I remember early touch screens, it is two independent resistive paths, a vertical and a horizontal, interpreted as coordinates by the ╬╝controller. I have a few 4-wire canibalized from old 'Palm' PDAs with need to put to some clever use...
    A larger area touched under the finger may alter the precision of the resistive reading. If such, the software may be set to ignore as a valid pin-point touch. Have you measured it ?

    ----> https://www.sparkfun.com/datasheets/LCD/HOW DOES IT WORK.pdf

    ----> https://www.dmccoltd.com/english/museum/touchscreens/technologies/resistive.asp

    ----> https://duckduckgo.com/?q=resistive+touch+screen+working+principle&t=canonical&iax=images&ia=images

    Data sheets ----> https://www.datasheetarchive.com/resistive touchscreen-datasheet.html
     
  3. matmat9090

    matmat9090

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    0
    Oct 18, 2018
    Thank you very much for you reply the information you put up is very useful.

    i haven't got one yet most of my old scrap electronics is too low tech. i think its worth buying one for fun and seeing. I'm not too convinced it will work for my application though.

    I want to use it as a mat in my fridge to sense if the shelf is full or not, i.e how much of it has stuff on it. Its those damn spacer dots that will get in the way. i would not wire it up to dedicated touch screen hardware or software i would just take (i think) the top restive output and the bottom restive output and connect them in a simple voltage divider circuit. and measure the out put initially with a volt meter then if that works with a micro controller and so on.


    Thank you
     
  4. matmat9090

    matmat9090

    4
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    Oct 18, 2018
    like so maybe

    Impedance_voltage_divider_svg.png


    [mod note - resized oversized image]
     
  5. kellys_eye

    kellys_eye

    4,289
    1,143
    Jun 25, 2010
    Something like the membranes used under cheapo computer keyboards may be more useful. They have the actual 'dots' in an x-y matrix that you could access either directly (through the edge connector x-y connections) or via the data it generates if still connected to the (usual) COB device and PS2/USB output.

    Two such membranes would, theoretically, cover a single fridge shelf with a pretty good level of accuracy (distance between keys).
     
  6. matmat9090

    matmat9090

    4
    0
    Oct 18, 2018
    ohhhh i like it that's a pretty good idea.
     
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