Can capacitive sensors distinguish plastic bottles?

[frootloopz]

Hi!

This is my first time posting here in the EDA board, and i hope you guyz could help me on this one, since this is crucial for the success of my pending undergraduate thesis.

Are capacitive sensors capable of detecting and distinguishing bottles according to their resin type/material? - for example can it differentiate a PET (polyethylene terephthalate) bottle from the one that is made out of PP (polypropylene)??

Hope that you post any opinions, suggestions, regarding this matter - and if also there are other economical/cheap/affordable ideas that you guys could suggest for me to be able to distinguish plastic bottles accdg. to material, please post it. Thank you very much!!!

 

[ionp]

This sounds extremely difficult.
I picture empty bottles on a conveyer belt, with capacitor plates on either side.
The effective dielectric in such a case would be mostly air, and invariant with changes to the plastic composition.

If you could fill the jar with a conductor fluid (saltwater?) as one electrode, so that you have a situation more like a leyden jar, then perhaps you could make something work.

Is that a possibility?

 

[frootloopz]

Thanks for the idea!

We'll try to consider that one; actually, what we are proposing for our thesis is a reverse vending machine that trades in PET bottles for rewards/incentives here in the Philippines.

So if you have more ideas, please feel free to post them, thanks!