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What sensors could I use to Differentiate between glass, plastic, and aluminum — Parallax Forums

What sensors could I use to Differentiate between glass, plastic, and aluminum

A.H.A.H. Posts: 2
edited 2009-11-23 21:51 in BASIC Stamp
As a class project we are having to do the ASME competition of an automated recyclable sorter using the basic stamp. I had a few ideas of using infrared to try to differentiate between the different materials but are there any suggestions on ways i could differentiate between the materials?

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-11-23 01:04
    How are the materials being presented? In a heap? Spread over a conveyor? Single file on a conveyor? Manually, one at a time? Knowing this will help to determine a reasonable approach.

    -Phil
  • A.H.A.H. Posts: 2
    edited 2009-11-23 09:08
    Phil,

    The materials will be presented single file on a conveyor belt through a hopper. My plan is to have all my sensors in a line on the conveyor belt.

    Andrew
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2009-11-23 14:07
    Just thinking out loud.... could you use some sort of heat detection, since each of those materials will have a different coefficient of heat transfer/absorption? Perhaps a sunlamp on the conveyor just to heat them up a little, and a combination of our IR thermometer shortly afterward on the conveyor.

    www.parallax.com/StoreSearchResults/tabid/768/txtSearch/Temperature/List/0/SortField/4/ProductID/539/Default.aspx

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  • Larry~Larry~ Posts: 242
    edited 2009-11-23 15:33
    Another outloud thought

    using a light (maybe laser)

    1······ glass would let light pass

    2······ aluminum may reflect light

    3······ plastic would do none of these
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-11-23 17:43
    All of these items could have labels on them, either paper or silkscreened. The items could be intact or crumpled. All these things conspire to make optical sorting very difficult. For aluminum, some sort of inductive detector would be the most relable, I think. Glass and plastic are more of a challenge. There's clear plastic, and there's dark and opaque glass, and vice-versa. X-ray fluorescence might work, but that's beyond the scope of a class project.

    -Phil
  • Larry~Larry~ Posts: 242
    edited 2009-11-23 18:17
    Not knowing what these items are, shape, size, color, makes it hard for exact answers but what is the differenance in the weight of each item.
  • LeonLeon Posts: 7,620
    edited 2009-11-23 18:56
    I would think that the samples are different shapes, sizes and weights, for a competition of this sort. People are very good at sorting stuff like that visually; machine vision would be an interesting, albeit difficult, approach. You won't do that on a Stamp, of course.

    Leon

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    Post Edited (Leon) : 11/23/2009 7:02:26 PM GMT
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-11-23 21:11
    For glass and plastic, a puff of air and a motion detector might help to distinguish the less dense plastic from the denser glass.

    -Phil
  • skylightskylight Posts: 1,915
    edited 2009-11-23 21:51
    light sensor and voltage sensor

    glass no voltage passed but light yes
    plastic if opaque or black no voltage and less or no light
    aluminium voltage but no light
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