Detecting metals, plastic, and paper

Hello!

My friends and I are going to make a project for or high school research class about segregating metal, plastic, and paper.

Its supposed to collect the waste then segregate it. We were thinking of using a Capacitive Sensor to detect plastic waste and paper waste and an Inductive Sensor to detect metal.

The problem is we don't know how to use the capacitive and inductive sensors to identify the said waste :sweat_smile: :sob: .
Should we use a different sensor? Please give us advice. If you know how to use the capacitive sensor and inductive sensors please tell us, we really don't have much resources for information in our school so we just rely on the internet :sob: .

Thank you so much and God Bless ! :smiley:

Define "waste". Will you be sorting crumpled sheets of paper or bundled magazines, large chunks of plastic foam or thin plastic bags, automobile carcasses or scraps of aluminum foil?

An inductive sensor could be used to detect metal, but the range is usually very short (a few mm).

I doubt that you will find any sort of sensor that would reliably discriminate plastic and paper, and both come in many forms.

Jam_B:
Hello!

My friends and I are going to make a project for or high school research class about segregating metal, plastic, and paper.

Its supposed to collect the waste then segregate it. We were thinking of using a Capacitive Sensor to detect plastic waste and paper waste and an Inductive Sensor to detect metal.

The problem is we don't know how to use the capacitive and inductive sensors to identify the said waste :sweat_smile: :sob: .
Should we use a different sensor? Please give us advice. If you know how to use the capacitive sensor and inductive sensors please tell us, we really don't have much resources for information in our school so we just rely on the internet :sob: .

Thank you so much and God Bless ! :smiley:

So you want to do this project but you got nothing. So rather than going and learning you just come here and ask us to solve it for you. That might get you through school, but there's a tough lesson waiting on the other side if you do things that way in school.

This issue has been solved over and over and over. They do this in recycling centers all over the world. Why don't you look for a little while at the many ways in which they've solved the problem.

jremington:
An inductive sensor could be used to detect metal, but the range is usually very short (a few mm).

I doubt that you will find any sort of sensor that would reliably discriminate plastic and paper, and both come in many forms.

I’ll keep that in mind. Thanks for the advice! :smiley: have a nice day

Delta_G:
So you want to do this project but you got nothing. So rather than going and learning you just come here and ask us to solve it for you. That might get you through school, but there's a tough lesson waiting on the other side if you do things that way in school.

This issue has been solved over and over and over. They do this in recycling centers all over the world. Why don't you look for a little while at the many ways in which they've solved the problem.

That's why I posted here because my friends and I have already searched and studied about this project from the resources that we were able to access. By the way were just junior high school students and we don't even have a robotics class or a working robotics club/group. Even some of the materials are not available in our place, but because we want to do this project and because we are VERY interested in programming and such we really are motivated in finishing the project. Even teachers
know only little (and somehow we know even more than them, which is weird btw).

Not to mention we spent weeks in trying to find a skilled and experienced electronics engineer, till we found a good one. I posted here just to make sure about the sensors we will be using. And again I am not from a country/place that's profound in the subject of technology or robotics, If we had more sources we would have finished this months ago. And its not like I'm finding the easy way out, I (and my friends) really love cracking my (our) head(s) up in solving problems (it's fun) that's why we chose to do this project. And I am seriously jealous of those who do robotics as a hobby (I'm only up to programming as a hobby), because we DON'T have resources

And I am not asking for you guys to solve it ok? This is just one feature of the project we are making, cuz this is the only one we can't seem to figure out cuz it's not in the internet (or so as we have searched again and again using so many combinations of words in google). Don't lump me in to those guys who asks stupid obvious questions. If this question has an obvious answer for you, then I'm jealous.

Also I'm sorry for this long (idk what to call it) umm reply. I just don't liked to be subjected as a person who didn't worked hard in school, cuz really if in your country students there have a sufficient amount of time to sleep, we don't. We rarely have a nice rest. Our time is not enough for us even in weekends cuz we still do stuff for school. And as a person I have never used someones work as mine just to get by.

I really thought that I could ask questions in this part of the website.

Again sorry for this long stuff. And sorry for the somewhat, somehow rude (I think) reply. I just somehow don't like what you said even if you are older, and I do have respect for people older than me btw. So well I am also sorry for wasting your time. If you didn't want to answer my question then please don't write your assumptions about me, I really would appreciate it.

I guess I should still be thankful of you for making time in reading my post. And also I know you're giving me advice that would be best for me (in your opinion), I'll just say thank you for your care. (It's just your way of telling me your 'advice' is what bothered me)

P.S I am only fifteen
P.P.S I am not a genius
P.P.P.S I never took proper classes in robotics nor programming
P.P.P.P.S I program stuff in my free time (random stuff) and its not by using automatic applications that gives you the freaking code but actual programming with an actual programming language
P.P.P.P.P.S I am not even from a country that has English as their language
P.P.P.P.P.P.S Not to mention as a 'not enough resource' that would also include Internet Connection , or even wifi. It's somewhat rare to find a connection that could load a website easily, we can use the computers in school but most use it in playing games so the internet could get pretty shitty. Even the internet in my home should be 10 Mbps (approximately) but I can only get a maximum of 5 Mbps of download speed. So all in all our sources are really limited.

Your English is very good! The problem is quite a few others have posed the same question on the forum and have had lengthy responses. You have not been able to find them, I guess.

Paul

If there are any waste separation plants in your area (they can not be found just anywhere, many countries don't have them), do give them a call. Chances are they are more than happy to receive a group of interested secondary school kids. Talk to your teacher and you may turn it into a class outing.

Then the separation itself. Having worked in recycling I can tell you it's very very very difficult (and with what I read from you, especially the "no resources" part, maybe the best advice is "don't bother") to separate materials reliably using machines.

Metals are "easy". Magnets and eddy currents are the common way. Magnets (of the very strong kind, hung above the belt where your trash goes) pick up most ferrous metals (some stainless steel alloys are not magnetic) and some others such as nickel. The rest can be sorted by eddy currents, basically a strong fast changing magnetic field, that quite literally shoots the metal parts from the belt, and in the process sorts the metals by the distance they fly. Then there's still metal left: bonded to other materials, or drink cans that people stuffed other things in.

Paper and plastic are a problem. These are normally sorted by hand (visual). You could (in theory at least) do it by pointing a camera on your conveyor with trash, then do some high end image processing, and have robot hands pick up and sort the pieces. Even blowing them off wouldn't be reliable as you'd blow other trash with it.

Then to be able to recycle plastics to a usable quality, you have to sort hem at >99% accuracy. That is usually again done visually: bottles are PET, buttercups and coffee cups are PS, garden chairs are HDPE. That results in pretty well sorted material, but there's still the problem of attached bits and pieces such as metal screws in the plastics.

Identifying plastics is one of the hardest problems of separating trash. The best way is probably using IR, and then measuring the absorption spectra which are unique for each type of plastic. Next is the problem of picking up that one piece of plastic, and not grab other pieces with it. Many products contain multiple plastics: the PET bottle with PP cap and HDPE label (or, far worse from a recycling perspective, paper labels even!). Many plastic film is multilayer, 5-10 layers is possible in that very thin cookie wrapping.

On top of that there's the hygiene problem, such as rotting food waste in the trash. Not only does it stink (big time), it fouls everything making it even harder to distinguish what is what as your clear PET bottle is suddenly not transparent any more, so you can't even look for that. It also messes up the IR spectrum measurement, if you were to try that.

The above is why there's so much onus on separation at the source. Having ten garbage trucks picking up ten different fractions of garbage is so much more efficient than having one truck picking up everything and trying to sort it later.

Use the search.

If you did, you might find the other 1000 threads explaining why you can't do this with an Arduino.

The only way this will work for a 'project' is if you know ahead of time the size, shape, weight, and/or color of the samples you'll be distinguishing. Obviously this project does not scale to the real world.
What would your 'project' classify an Arduino board as? Metal? Plastic? Paper? Glass?

wvmarle:
Metals are "easy". Magnets and eddy currents are the common way. Magnets (of the very strong kind, hung above the belt where your trash goes) pick up most ferrous metals (some stainless steel alloys are not magnetic) and some others such as nickel. The rest can be sorted by eddy currents, basically a strong fast changing magnetic field, that quite literally shoots the metal parts from the belt, and in the process sorts the metals by the distance they fly. Then there's still metal left: bonded to other materials, or drink cans that people stuffed other things in.

The way I have seen this done is a conveyer belt raises the stuff and shoots it off the end. while falling, the magnets and eddy current devices deflect the metal into a collector while non-metalic goes into a different bin.

Stuff has to be dry to function and all clogging up material removed by hand.

Paul

I know this is an old post but there's a trend that bothers me and I want to point the obvious out:

People ask a question only to be slammed for asking it.

Why not explain that to properly explore this experiment and others is to try different things. If you have an idea and a problem, you can explore a possibilities of a solution.

Break down the problem; ask questions and find solutions. For example here, maybe try to find an inductance for plastic, or maybe a signature. Everything has a "frequency" so maybe plastic can be detected at a partial wave-length.

Just saying... Break things down into small chunks and work on solutions to those chunks, sometimes the little problem isn't little and needs dissection too.

Anyway, I know that isn't a solution, but I guarantee not giving up is a solution (at least to one part of the problem). So don't give up and work threw the questions, one at a time.
Build the dream.
whatisacnc.com