Q&A for How to Build a Metal Detector

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What type of radio do I need?

Community Answer

AM radio brand doesn't matter, but choose a small one to keep the weight down.

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Question

Is it okay to use the radio on my cellphone?

Community Answer

No, the radio on your cellphone can only receive FM whereas you need AM for this project.

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Question

How do a calculator and a radio attract metal?

Michael Tillman

Community Answer

The apparatus does not attract metal. It sends out electromagnetic waves that get bounced back to the antenna, changing the tone as it detects metal.

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Question

Is it okay to use a big radio?

Michael Tillman

Community Answer

Possibly, but you may not be able to clear the static with a large radio. You would have to use trial and error to find out if it will work. You are looking for a specific tone.

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Question

How may I create a single circular metal sensor that will close a switch when the metal passes over it, from center to perimeter, and then opens the switch on its return swing, perimeter to center?

Community Answer

You could use a brick wall high pass filter. You could have a low voltage relay switch that only closed when it had electricity running through it. Run the audio that you would have just listened to through the relay. You could control the sensitivity by changing the frequency cutoff of the limiter. And use that to run your switch. Probably would be better with two coils though.

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Question

Will this metal detector detect aluminium?

Michael Tillman

Community Answer

Yes. Aluminium is diamagnetic, which means it would be affected by the metal detector. You can test it with a soda can.

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Question

When assembling the metal detector with the calculator and radio, can I use an AM/FM radio, or do I have to use an AM radio?

Michael Tillman

Community Answer

You can use either one. All that is required is for the radio to be capable of tuning to AM radio. It is better to have an external antenna though.

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Question

Where do I put each part?

Community Answer

Check out the pictures.

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Question

Where can I buy a small radio?

Community Answer

BestBuy or any other store that sells electronics would be a good place to start. You could also try Amazon or other online retailers.

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Question

How far deep will this detector penetrate?

Michael Tillman

Community Answer

The depth penetrated depends on the strength of the magnetic field and the composition of the medium you are trying to detect through. This is more complex math and takes more time and expertise than the average person has to put into detecting surface metal.

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Question

My radio and calculator won't produce the humming sound. What am I doing wrong?

Michael Tillman

Community Answer

The calculator mostly creates a small magnetic field that interferes with the static and creates a humming sound by the antenna. You want the calculator's power circuit as close to the antenna as possible, so try moving it closer.

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Question

What does the calculator do in this metal detector?

Michael Tillman

Community Answer

The calculator creates a small electrical field that interferes with the static, allowing the radio to pick up short range interference shot back to the antenna by the metal.

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Question

Can I make a metal detector without an AM Radio?

Community Answer

No, you must use the AM or FM/AM radio because FM's can't get the tone and AM's can.

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Question

Is it possible to make a metal detector for aerial search-and-rescue?

Archie !

Community Answer

Yes, but it would need to be a lot bigger, possibly an antenna. The person who you hypothetically are searching for would need to be carrying metal objects, and your detector would need to be long/deep range.

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Question

How deep will a metal detector penetrate?

Community Answer

The depth penetrated depends on the strength of the magnetic field and the composition of the medium you are trying to detect through. This is more complex math and takes more time and expertise than the average person has to put into detecting surface metal.

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Question

Can this simple method detect gold?

Community Answer

It cannot because gold is a type of rock. There might be types that can detect gold but this type will only get you metal.

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