How can i make a metal detector

		Quote:			Posted by goldigger
	I had trouble with the last post because the system said I had already posted it! Sometimes this system plays little tricks, too. goldigger

When that happens, use your browser "Back" button and then use the forum "Preview" feature. Saving it that way gets rid of the problem.

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		Quote:			Posted by xavier
	Hi Goldigger I build an adapter for my DVM (inductor)and it works fine I also found a diagram of a frequency counter that I would like to adapt to the adapter for the DVM however I could not get the led display and I was wondering if I could adapt an  LMB 162A display with an ICL7106 CPLZ driver in fact it was given to me at the shop where I get my parts they ordered some for a school and I guess that they had some to many so they gave me one display with a driver and I really would like to find a use for it ho yes it is dual line display. Here is the link to the site where I got the frequency meter diagram. Best regards Xavier

This is getting outside of the topic subject by quite a bit. Don't take this the wrong way, Xavier, but if you start a new topic about tools needed to build a detector your posts won't get lost in the midst of a seemingly unrelated area. You may certainly keep the discussion here about LCM meters as it is on topic but a new topic will get it more focused attention.

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		Quote:			Posted by xavier
	Point taken thanks GD

Even better still, you get more points for starting a new topic! How cool is that?

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Xavier, there are some really good books in this world on coils and electromagnetic devices. Start with the ARRL Antenna Handbook, available second hand the world over. That book contains everything you need to know about coils used as antennae including how to develop a Smith Chart from measured field strength readings. After all, a coil is nothing more than a transmitting and receiving antenna. Do you know where a metal detector coil's strongest field is? The weakest?

The answer may shock you but the strongest Tx field is around the edge of the coil. The weakest is above and below the coil. The shape of the field is like a donut around the coil, not a round sphere like the cartoon drawings show you in the metal detector theory pages that you find around the web. A good coil will have the addition of a Faraday shield around the edges to minimize the field generation around the edge which also has the ability to sort of focus the field a bit more towards the area above and below the coil.

I'm not trying to tip over any sacred cows here, mate, but the real answers will be in the book I recommended to you. Order one or go to your library. They are in the Amateur Radio section in the library and can be purchased at any local shop that sells radios.

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Homefire, I was pretty eager to get my 15 when I first got here but I've been on many forums and did it the hard way. Being conversational, even in a limited way, is far better than just running around putting an emoticon on to 15 topics.

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