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 :
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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

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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


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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
catsy272 months ago

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 :)

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

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

Aditya M3 months ago

Fabulous,thanks for the idea!!!

Very nice,what an easy way to make a ditector!
chuckcrunch2 years ago
nice gag , the beeping is a give away LOL
mayang062 years ago
would there be a great difference if i use am/fm radio along with the calculator as my metal detector?
ochoa102 years ago
Maybe it works better with a calculator without cell?
win nyunt2 years ago
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.
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?
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.
jon-ecm3 years ago
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.
rscott-23 years ago
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.
thx alot
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.
Wow, thats clever.
riverreaper4 years ago
do studfinders work the same way?
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...
amazing im trying this out
FFVIIBOY4 years ago
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 :)
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???
does this thing really work???????????????????????? answer now
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_man15 years ago
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.
oregon_man15 years ago
HMM? Where do I start? To anyone who fell for this trick, this kid has got you buffalo'd. Take a closer look!!! He's using his thumb to press the buttons of the calculator as he passes it over the spoon!!! LOL!!!
yoitspoe5 years ago
dude this works! i tried it with a basic sony calculator and a scientific calculator, a texas intruments ti30xa. and to answer someone elses question, yes it does work with radios with headphones and radios with speakers
polar bear66 years ago
(removed by author or community request)
To quote wikipidia: “Faraday's law of induction (or the law of electromagnetic induction) states that the induced electromotive force in a closed loop is directly proportional to the time rate of change of magnetic flux through the loop.” I believe that both the calculator and the radio are closed loops. A metal object (such as a spoon) would create a magnetic flux in the magnetic field of the loop. The radio, once tuned to the magnetic field of the calculator, should pick up any fluxiations in the calculators magnetic field. If you have set it up correctly I believe that the theory behind this is sound. Did you just read wikipidia and decide he was a fake because it did not mention a calculator or a radio receiver?
when you put it like that man it sounds pretty real, maybe i jumped the gun on this one. after trying to charger your ipod with an onion and making a speaker from a penny, you see "hacks" in a different way. i still have nightmares about that onion, crying to the smell om Gatorade is not a pleasant thing. if i find me one of them lil radios i will try this, i have a calcubator right here. sry bout the yelling and cursing.
for real, I tried that crap too. That penny speaker thing drove me crazy. I thought I would never hack again.
What penny speaker?
ahh well you cant give up but you have to use your brains on some of the hacks.. come on a penny speaker?? charging your ipod with an onion and gatorade ?? use more sense than that :P
But are you aware that the metal object doesn't have any magnetic flux to begin with because it doesn't have a magnetic field? Or so your statment is misleadingly making me say that...
SeaLion SeaLion6 years ago
Edit: I'm not saying that your instructable is fake or anything, I am quite happy to try it and go *awesome!* at it, but what topmonkey is saying is phrased such that it kinda defies the physics I spent 3 weeks learning - Magnetism, which includes electromagnetic induction.
RazorG606 (author)  polar bear66 years ago
I feel sorry for you. If its so fake, how the hell can it be in a book sold on called sneaky uses.
Ive noticed when you point a t.v. remote it will make that same noise as yours did with the calc., when you push and hold the volume button,Im gonna try that with a radio and see what happens also.
can it work for stuff underground
no i definately want that book
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