View Full Version : What sensors could I use to Differentiate between glass, plastic, and aluminum

11-23-2009, 07:19 AM
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?

Phil Pilgrim (PhiPi)
11-23-2009, 08:04 AM
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.


11-23-2009, 04:08 PM

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.


Beau Schwabe (Parallax)
11-23-2009, 09:07 PM
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 (http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/Temperature/List/0/SortField/4/ProductID/539/Default.aspx)

Beau Schwabe (mailto:bschwabe@parallax.com)

IC Layout Engineer
Parallax, Inc.

11-23-2009, 10:33 PM
Another outloud thought

using a light (maybe laser)

1ииииии glass would let light pass

2ииииии aluminum may reflect light

3ииииии plastic would do none of these

Phil Pilgrim (PhiPi)
11-24-2009, 12:43 AM
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.


11-24-2009, 01:17 AM
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.

11-24-2009, 01:56 AM
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.


Amateur radio callsign: G1HSM

Post Edited (Leon) : 11/23/2009 7:02:26 PM GMT

Phil Pilgrim (PhiPi)
11-24-2009, 04:11 AM
For glass and plastic, a puff of air and a motion detector might help to distinguish the less dense plastic from the denser glass.


11-24-2009, 04:51 AM
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