Electronics > Beginners

Good starting place to learn about metal detection systems

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Infraviolet:
I'm interested in building a screw detector as part of a larger project, and want to learn as much useful new stuff along the way as feasible. My interest is in making it as small as possible and detecting fairly small screws, but only at close range. I have looked online for circuit exmaples but don't want to just copy, I want to learn some stuff along the way. I have several years of general electronics and embedded programming experience, and have made a variety of analogue and digital projects before, usually custom sensor systems interfacing in to microcontrollers and on custom board designs. Could anyone advise of a good place to start looking so I can put myself on a path towards developing such a system? Again I'm not after answers, but introductions so I can have the satisfaction of working out answers for myself.
Thank you

Manul:
Through my experience related to metal detectors (I design and build them as a hobby), I never found good comprehensive sources on the subject (like books, or web pages). Maybe there is, but I just don't know. There are some information available if you search more specific topics, like for example how to build a high performance search coil, ways of implementing ground balancing, etc. So what I suggest is to assemble your knowledge methodically and step by step. First search what kind of technologies are used today or were used historically. For example induction balance, pulse induction, etc. Then narrow your search about one specific technology, see articles, schematics, patents. Narrow the search even more and learn specific topics.

You will get general idea relatively quickly. In the end it boils down to circuit design. This subject is as wide as the electronics itself. While trying to design a good metal detector you will easily burry yourself into noise and stability problems, filters, thermal EMF effects, digital signal processing and who knows what else. But these are general electronics topics.

By the way, there is such thing as induction proximity sensors, which might be good for your application. It would be much more time efficient and robust solution if you could use something of the shelf.

kripton2035:
https://www.geotech1.com/cgi-bin/pages/common/index.pl?page=metdet&file=projects.dat

ledtester:
DiodeGoneWild just recently posted a series of videos on metal detectors.

The first one analyzes how a cheap $2 kit works. He then goes on to present his own design.

- Building a metal detector & how does it work
https://youtu.be/Bs9U15qQo0E

- DIY DD metal detector 1 - first success
https://youtu.be/eCRgNr6jj2g

- DIY DD metal detector 2 - coin at 35cm, audio indicator, PCB
https://youtu.be/-czOV-hKSlA

Infraviolet:
Thanks for the links

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