Introduction: Turn a Calculator Into a Metal Detector

Picture of 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 :

Step 1: What You Need.

Picture of What You Need.

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

Step 2: Let's Begin

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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

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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

Picture of 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

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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

Picture of 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



jompon2547 (author)2017-11-10


ContonioB (author)2017-02-21

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.

Silversalmon (author)2016-03-18

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.

GODISMYSAVIOR (author)2016-03-11

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

GODISMYSAVIOR (author)2016-03-11

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

GODISMYSAVIOR (author)2016-03-11

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

rscott-2 (author)2011-03-11

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.

KateKat357 (author)rscott-22016-02-11

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

JMBYR (author)rscott-22016-01-01

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

We just did the exact same thing...finding Yorbo!

beer-liner (author)2015-10-14

"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.

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.

ManojK75 (author)2015-12-15

Why calculator is used in this circuit of metal detector

Daniyal Khan (author)2015-11-18

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

ZahirA1 (author)2015-07-20

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

haywoodyoudome (author)ZahirA12015-08-02

Work on your English so people can understand what you're trying to say.

DonnaR1 (author)2014-12-18

i am making this..but does it actually works?

ZahirA1 (author)DonnaR12015-07-20

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

avichal51604 (author)2015-06-17

avichal51604 (author)2015-06-17

ridge2244 (author)2015-05-23

Tried it. Yes it works.

For Better Or Worse (author)2010-07-09

SergentLaughter, Try taping one or more of your calculator buttons down, that should do it ;) Oh ya, RazorG606, nice idea but it is already all over the net. Another Thing is that yes it is a metal detector, but the range of this project is too small for anything other than finding coins in the sofa and studs in the wall. But still, if you hacked the radio to give more reception and then put aluminum in the calculator, then put a faraday sheild in between the two devices, the range should increase enough to match a full scale one. P.S. If you try to make the excuse that I do not know what I am talking about, you should know that I did your project a billion times (maybe not a billion, but close enough) and I'm a jack-of-most trades. Meaning, I can make or repair ANYTHING you can THINK of. So that being said, hope you take my advice, at least with the faraday shielding. That should make the most diference in range. I hope by the time you get to the end of my comment, you do not take offence of my p.s.. You see, people seem to think i'm stupid and a was just clarifying the reverse of that. Hope to talk soon, For Better or Worse

Lol, right next to your JACK OF MOST TRADES(who can fix anything on god's green earth) award you can put your humility award as well.

AltonW (author)Riptide1002015-04-24

I know it's 3 years old but I have to say: LOL..Good one!

ginoom (author)2014-10-27

ive tried it,am/fm radio and calculator but it ddn't work, does it needs to select w/ calculator and radio i must use?

TheMaster11 (author)2014-10-14

did not work.

hummerh2sut (author)2014-07-14

This sucks nobody try this. does not work at all. bought a radio and went to the beach tried it out and there you have it $15.00 Down the tube. Razor g is a scam

catsy27 (author)2014-05-11

This is really cool :) I lost my quarter and instead of digging between the cracks of my couches I finally had something to help me find it lol :)

KevinAlien26 (author)2011-08-20

Hey great 'ible even though u only found a spoon from a few inches away it's a good place to start :)

cheezyguy5 (author)KevinAlien262014-04-08

Put an electro-magnet behind the radio and it will be MUCH stronger, there will be alot more edicurrents generated.

Aditya M (author)2014-03-28

Fabulous,thanks for the idea!!!

faisal rahmanp (author)2012-09-20

Very nice,what an easy way to make a ditector!

chuckcrunch (author)2012-06-10

nice gag , the beeping is a give away LOL

mayang06 (author)2012-03-09

would there be a great difference if i use am/fm radio along with the calculator as my metal detector?

ochoa10 (author)2012-03-08

Maybe it works better with a calculator without cell?

win nyunt (author)2011-11-03

I am very happy. I have not money.If have money,there is not eassy to buy this b/c of my country. I very thank to you.

bbuuggmmeennootta (author)2011-08-12

And just to clarify before the trolls jump on this and attempt to disprove things based on one small formality..

(you notice I gave you the preview of that url, that's cause I know how ppl are with redirector sites, so before you say Hurr Durr, just check em)

The TI-108 unit is solar powered and does not use a battery to power it. (from TI's knowledge base)

So no that calc in the video DOES NOT have a battery. Still, it is able to use the ambient light (carpet doesn't have to be 'reflective' for light to be available in the room, as a matter of fact, solar calculators require very little power) in the room to function.. How amazing is that?

jon-ecm (author)2011-04-15

Thanks for the good info.
I published a website that has guides to making a more advanced pulse induction metal detector based on the same technology found in minelabs gpx series gold detectors. It's really easy to build and I'd defiantly recommend it to someone who has some electrical skill.

peterkharofeh (author)2010-04-10

thx alot

aqwiz (author)peterkharofeh2010-12-26

Wow, I didn't know the OP was an Alot. That's really weird, I didn't even know the Alot species was capable of intelligent thought.

chemicalvamp (author)2010-11-27

Wow, thats clever.

riverreaper (author)2010-07-17

do studfinders work the same way?

For Better Or Worse (author)2010-07-09

Oh ya, RazorG606, I forgot to mention that if you are interested in stuff like this, Try Making my analog Transmitter from random things. It needs some improvements, like faraday shielding. Hope you leave plenty of comments for me.. One other thing, if you do not know what a faraday shield is, it is usually a steel sheet or mesh that is grounded to the negative of the battery terminal or is earthed. Hope this helps. For Better or Worse...

iloveemogirls (author)2010-05-13

amazing im trying this out

FFVIIBOY (author)2010-03-16

Well i just need to get a calculater and a AM radio or watever its caled and try it out. ill tell u wat hapens wen i do it :)

mastermakoko (author)2008-11-13

man.......i tried to make this thing and yes it does make a loud noise when close to a calculator......but it doesent make a ring voice when near a metal any ideas???

mastermakoko (author)2008-11-08

does this thing really work???????????????????????? answer now

sergentslaughter (author)2008-10-14

I tried this and could not get this to work all i would hear is a tone every time a key was hit on the calculator and that was it...Any advice?

oregon_man1 (author)2008-10-14

of course, there is no video here at this site. but if you go to, you can see the full length video of this prank. Please do yourselves a favor, watch the video, take a good look at him passing the metal detector over the spoon.

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