How to make a metal detector? :unsure:

[Daan]

Hello Everyone,

We're students from Nijmegen, The Netherlands. In this final period we have to make a episode of "Klokhuis", a program that explains certain subjects to kids aged 10-13. As a subject we chose metal detectors. About half an hour ago we decided we'd try and make our own metal detector, but we failed, big time!

We used two coils, a big one and a small one, and put the small one in the big one. We hooked the big one onto a alternating current of 12V and the small one to a voltmeter with a capacity of 100 mV. We created the coils ourselves by spinning a (plastic coated) wire around cardboard toilet rolls. When we turned it on and put some metal near it, nothing happened, it only got really hot.

So, our question is: How does one make a simple metal detector, by just using coils?

We're using this simple metal detector to test out which metals can be detected.

Thanks in advance,

Daan, Alex, Hidde and Harm.

 

[Captain Kirk]

Daan;

You need to understand the principles of any subject before you try to teach someone else. Do a Google search for metal detector design. Designing metal detectors is much more complicated than just winding two coils, exciting one and picking up the signal with the other one.

Glenn

 

[bazooka]

Firstly, I wish you luck in your endeaver.

I wouldn't use AC, but DC instead. I think it would be much safer and easier to control electronically.

The machine that would be the simplest to build I would think would be a pulse induction machine. This uses a single coil that transmits and then listens for a response from any metal that may react to the EM transmission. Of course it does this many times a second on a standard machine, but this may get you started in the right direction. Am I an electrical engineer? No, but I did stay at a Holiday Inn Express.

 

[Andy Sabisch]

Daan,

There are several different designs of detectors but the oldest and easiest to make is called a Beat Frequency Oscillator or BFO for short. There are several links to sites where you can build one including the following:

The following links are for a real basic / non-BFO detector:

http://www.ehow.com/how_2198978_metal-detector.html
http://lifehacker.com/359432/build-a-metal-detector-on-the-cheap

Here's some that will enable you to build a functional detector . . . . .

http://www.easytreasure.co.uk/bfo.htm
http://www.instructables.com/id/bfo-metal-detector/
http://gpex.ca/smf/index.php?topic=48.0

Hope this gets you and your class on the path to build a working detector . . . .

Andy Sabisch

 

[Daan]

Thanks allot for your replies, We're working on the script now and we'll start filming in 2 weeks (after our well earned holiday! ). I plan to continue researching the DIY metal detector next week, and hopefully build a working one. Seeing as Chemistry is my main interest / subject, the physics around building one are looking quite challeging. Especially the 'simple' electronics cards.

My task now is to research how these things work, and rewrite it so that the young minded will understand it.

I'll keep our progress posted here if anyone's interested .

Happy metal hunting!

Alex

 

[legal_in_usa]

Please keep us posted Daan,I would love to see how it turns out .......I'm an industrial electrical engineer.and consultant...I built one in college years ago....you will want to use DC voltage....how ever i cheated cause i used an oscilloscope. I do know the most important is the windings of the coil.Please update us ......Thanks