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Topic: Keeping silverware out of the trash- metal detection style. sensors? EMF? WHAT? (Read 2 times) previous topic - next topic

SykoMiko

Hello everyone this is my first time here! I am interested in electronics, talked about getting an arduino for years, and recently bought one for myself!

I need all your help in guiding my first project in the right direction!

The main goal of my first project is to keep silverware out of the trash at work. I work at a restaurant, and a lot of silverware gets thrown away on a daily basis by accident.

My idea is to tune some type of metal detection to pick up when a silverware passes by into the trash can. If I can get the arduino to recognize the silverware passing as a certain numeric value, I can use that value to tell the arduino that it's time to sound a buzzer and flash some lights. And yeah basically the idea is a metal detector fit over a trash can lid.

So here's the problem. I did a bunch of research on how metal detectors work, and came up with a bunch of information. I found this project which makes me believe this is feasible: http://www.youtube.com/watch?v=Rf-FbK8ieHY
I've been reading this article too http://www.deeptech-bg.com/Tumanski.pdf which has a lot of great information, I just don't know how to interpret this into something I can use for my project. I don't want to make something more complicated than I have to, so any insight you may have would be greatly appreciated!!!

I don't have time at the moment, but I have done some more research, and can explain a little more about what I think I know about VLF, and EMF detection, which may help you help me more. So i'll post more tomorrow, and hopefully get some feedback in the meantime.

Thanks!  :)

SykoMiko

Just found this also:
http://electronicdesign.com/components/consider-all-factors-when-selecting-proper-inductive-proximity-sensor

This article definitely helps me realize I have to utilize the right sensor and design. I have a specific goal of detecting one type of object, so it should be pretty easy  :~. I just have to understand the principles on how these types of sensors work, and go from there. Any insight would be appreciated!

Erdin

That video does not show a metal detector.

To detect metal, you need some extra hardware.
Can you make a big coil over the trash can ? Just wind a long wire a number of times (5 to 100) around the top of the trash can. You need a circuit that puts a RF signal on the wire and detects a disturbance.

Since the metal is going through the coil, it will be easily recognized.

This is a normal metal detector circuit, connected to the Arduino.
http://dzlsevilgeniuslair.blogspot.nl/2012/06/metal-detector-for-bikes-and-cars.html

This creates a frequency in a coil, and the Arduino could detect a change in the frequency.
http://www.instructables.com/answers/Can-I-Connect-A-Metal-Detector-Coil-Directly-To-A-/

I think it would be possible to let the Arduino create a pulse for the coil, and detect the received pulse length. But I have not seen such a circuit yet.

The alternative is a compass and detect the disturbance of the earth magnetic field. But that would probably not work in your situation. Search for "HMC5883L metal detector" if you want to know more.

PeterH

I've seen a documentary showing a big restaurant doing this with a really, really big magnet to separate utensils from the food as it was thrown into the waste bin.
I only provide help via the forum - please do not contact me for private consultancy.

CrossRoads

That's what I was thinking - a big ass electromagnet to collect up any metal thrown in.  Silverware, rings, loose change, iphones, ...
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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