Sensors to detect Metal, Paper, Plastic, Glass, Wood

Hi! I am trying to build an automated waste sorter and in need to figure out what sensors I can use to differentiate between metallic waste from plastic from paper and wood. I have seen some discussions that seem to point towards inductive sensors to sort out metals vs non-metals first, then capacitive sensors etc. Does anyone know how I can do it. Thanks.

multiple sequential sensors eg: inductive sensors to sort out metals vs non-metals first, then capacitive sensors etc.

This is not an easy task. I do not know of any sensor that can distinguish plastic from paper or wood easily. From an electric view (conductivity, dielectric constant etc) the materials are just too similar, especially when in 'waste' form i.e. unknown shape and size. With some clever ultrasonic sensors you may be able to get some info about the materials density but there is plastic bags and paper bags that are about the same. So the only option I see would be an optical sensor of some sort. A spectrometer maybe?

If this is a commercial project, you may be able to afford the sensors to sort a waste stream.

If it is a small personal project, you will find very few sensors that can sort a moving stream of waste.

Weedpharma

Thanks for the feedback you all. I do not need to necessarily sort a 'continuous stream' of waste. Hopefully, that can be a goal for future projects. For now, I am interested in accomplishing at least placing different materials in relevant bins.

weedpharma: If this is a commercial project, you may be able to afford the sensors to sort a waste stream.

If it is a small personal project, you will find very few sensors that can sort a moving stream of waste.

Weedpharma

How expensive can these commercial sensors be? I tried looking it up to no avail.

Google is your friend, again. look at this page to get an idea of how material is separated commercially:http://wastersblog.com/604/waste-separation-methods/.

Paul