distinguish between plastic and glass

Discussion in 'The Projects Forum' started by Ilyas Ennaoui, Apr 29, 2018.

  1. Ilyas Ennaoui

    Thread Starter New Member

    Apr 29, 2018
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    Hello everyone .
    I am working on a project, and I stuck in one part, concerning, how to distinguish between plastic and glass, and papers if possible.
    what kind of sensors can I use in this case.
    thank you in advance
     
  2. jpanhalt

    Expert

    Jan 18, 2008
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    Welcome to AAC.

    Try the well know flame test. You can also measure refractive index and numerous other properties. Do you have any clue what the "plastic" is or even a good definition for "plastic" versus "glass." (FYI, a lot of compounds form "glasses." I assume you mean ordinary soda lime glass.)
     
    -live wire- likes this.
  3. Ilyas Ennaoui

    Thread Starter New Member

    Apr 29, 2018
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    Thanks for your answer.
    I want to make a Smart trash that will be able to sort these components
     
  4. jpanhalt

    Expert

    Jan 18, 2008
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    Can you give some more clues? Will the materials be in a single layer on a conveyor? Will they be crushed? One option is to crush the whole pile and use a sieve to sort out the smaller glass particles. Then use flotation for a final separation (glass is heavier than water; most plastics are lighter).

    What are you thoughts on what is beginning to sound like a homework problem?
     
  5. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    The best and most efficient way to sort it.....is three trashcans per house.
     
    Hymie likes this.
  6. -live wire-

    Active Member

    Dec 22, 2017
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    You can measure how reflective they are with certain sensors. Or, for plastic, it would probably float while crushed up glass will sink (in water). So you just need to crush it all up and pour it into water. Before that, try mixing it all up and blowing it all around. The light papers would fly around but heavier things would not. Then use huge induction heaters to melt all the metal recyclables after you take the other stuff out. As a bonus, the molten metal will melt the remaining trash that people threw in. This assumes there are also metal cans and stuff.
     
  7. DickCappels

    Moderator

    Aug 21, 2008
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    Just a guess but you will probably get good results measuring the propagation velocity of an acoustic wave, perhaps something as simple as hitting the bottle with a solenoid and watching the wavefront travel for a distance in the medium in question.
     
  8. Sensacell

    Moderator

    Jun 19, 2012
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    Measure the dielectric constant of the material in question.
     
  9. -live wire-

    Active Member

    Dec 22, 2017
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    If it is wet and dirty it would be influenced a lot, right? And do you mean the dielectric breakdown?:)
     
  10. Sensacell

    Moderator

    Jun 19, 2012
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    If the samples were clean and homogeneous, you would have a prayer, but with general garbage... no.
    A capacitive sensor can determine different dielectric materials, all other things being constant.

    http://www.clippercontrols.com/pages/Dielectric-Constant-Values.html
     
  11. ebp

    Well-Known Member

    Feb 8, 2018
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    In a heavily automated sorting plant I know of, glass is taken out early in the process with gravity sorting. Plastics are sorted late in the process using a conveyor, optical recognition and air jets. This is established technology in quite widespread use.
     
  12. wayneh

    Expert

    Sep 9, 2010
    14,850
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    Bingo. Let's not reinvent the wheel.
    I was thinking a fluidized bed, a column with upflow air and maybe an augur up the middle, would allow separation by bulk density. Glass would "sink" while anything plastic would "float". You then adjust the takeaway positions and rates and the thing can operate continuously at steady state.
     
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