Turn a Calculator Into a Metal Detector





Introduction: Turn a Calculator Into a Metal Detector

I recently discovered a really cool method in using a few household items to make a HomeMade Metal Detector! Heres how to make your own!

Heres a link to the video : http://www.youtube.com/watch?v=_G5HzeIl9cY

Step 1: What You Need.

All you need for this project is, an: AM Radio , some tape , and a small calculator.

Step 2: Let's Begin

Begin by turning the AM radio on. Tune it to the high end of the AM band, but not directly on a broadcast station. Adjust the volume to the maximum level so you can clearly hear the static.

Step 3: Positioning It

Now with both the calculator and the radio turned on, position the calculator close to the radio till you hear a loud tone

Step 4: Taping It Together

Once, this position is found, tape the calculator to the radio while maintaining the placement.
When you done taping it together, make sure its steady.

Now lets test it out.

Step 5: Testing It Out

Turn your radio on, and try the metal detector out on any type of metal. You will notice that the calculator beeps whenever you get close to metal. It beeps even faster the closer you get to the metal.

Step 6: Why It Works

The reason this works is because the loud tone coming from the radio is the calculators
electronic circuit producing a radio frequency signal. That being said, the radio waves from the calculator reflect off the spoon and are heard on the AM radio.

And there you have it, A cheap and easy homemade metal detector.

Enjoy, and have fun!

PS: If you like this instructable, please give it a nice rating. Thanks!

To see the metal detector in action, check out the video




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    172 Discussions

    This was from an episode of curious George. George the monkey lost his toy robot on the beach and the professor suggested george could make a metal detector this way.


    I tried making this detector a lot of different ways e.g. calc and radio back to back, with an angle between them using a cd case etc and have had no luck with it at all. I notice that a couple of people - like ridge2244 10 months ago said that it worked. What make of radio and calculator actually work together? Also does the beeping really speed up as the metal gets nearer to the radio? If I'm honest, I am feeling pretty sceptical about it at this stage! Has anyone else got it to work? If so, I'd love to hear which calc and radio you used and how you positioned them.

    I like this project and I am using it for a school science project.

    I like this project and I am using it for a school science project.

    I like this project and I am using it for a school science project.

    Ahahahahaha! I love the world sometimes. My son happens to be watching an episode of Curious George with this on it when I stumble to the page.

    4 replies

    I saw that same episode. Would be a good idea for a science fair 8-).

    That is exactly why I am here at 6:57 in the morning. George really peaked my curiosity on this one!

    The reason why I even looked this up is because my son was watching the exact same episode and I wanted to be sure if it really worked or not. haha

    "You will notice that the calculator beeps whenever you get close to metal. It beeps even faster the closer you get to the metal. "

    This was my first clue that this makes no sense at all. What would possibly induce the calculator to beep in the presence of a metal. Surely it would do so whether it had a radio strapped to its back or not. Never seen one do that yet.

    If it worked at all it would have to relate to signal strength received by the radio due to reflection or eddy current losses as the radiated noise approaches the metal. Then maybe there would be a barely audible change. It would be nice if there was some Beat Frequency or Heterodyne effect, but since the radio is not "Tuned" to the calculator's oscillator or any thing like that this is unlikely. This does appear to happen when buttons are pressed as has been mentioned by others, and that is not a surprise.

    B.S? I think so.

    1 reply

    Not quite.
    It is the radio that "detects" the metal, and the frequency IT makes just makes the calculator beep. The key is the radio. At least that is the theory.

    Still not sure if this works, but doubt it will work very well without adding a large coil.

    Why calculator is used in this circuit of metal detector

    Do we need a beeping calculator for this project or any would work ?

    I did not make .recently i involve heare but i need a long range one because iam in wonderland ..its really tresurs land i pound 74 sighns and codes .but i want perfact target ..plese anybody help me

    1 reply

    Iam zaheer from uper pak .its really historical sites for tresures .and i need a reall helpr intrest one plese