Picture of Simple metal detector
The other day when I was searching instructables I come across on interesting and simple circuit for metal detector. It is build with 555 coil and few other components. Instructable that inspire me to do this project was this one. Main debate was: does it really work? After quick research I found this video that proof it works. That was the time when I decided to make my own metal detector.

I do believe, that before you start working on metal detector you should read more about metal detectors and how they work.

I am not hold responsible for any damage that occurred during reproduction.
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Step 1: Parts and materials

Picture of Parts and materials
- 555
- 47 kΩ resistor
- two 2μ2 F capacitor
- 9 V battery, switch, battery cable and some wires
- buzzer
- 100 m of copper wire, 0,2 mm in diameter
- gaffer tape and wood glue

Instead of buzzer you can use 10 μF capacitor and speaker (8 Ω impendence).

- breadboard and wires
- pliers, tweezers, pliers for making holes
- soldering iron and soldering wire
- sharp knife, ruler, pencil and pair of compasses
- hot glue

Step 2: Schematics

Picture of Schematics
The idea is not mine. I found schematic on this page (there is also other 499 projects with 555). I only added switch beetwen battery and circuit and instead of speaker I am using a buzzer.

Step 3: Coil

Picture of Coil
The most difficult part is making coil. In great help was web calculators for air coils. With them, I calculated that with coil 90 mm width I need about 250 windings and with diameter 70 mm 290 windings that inductance can be 10 mH. You can also buy already made coils online.

I made coils core from cardboard. Coil is made from lacquered copper wire which is 0,2 mm in diameter. I did 260 turns. Before soldering, you must clean up both ends of coil. You can do that with help of sandpaper.

Step 4: Testing

Picture of Testing
I made circuit on breadboard because I didn’t want when PCB would be finished it wouldn’t work. You can see test in video bellow.

Step 5: PCB

Picture of PCB
Test was a success. Because of that I made PCB. I made it the same way that I made PCB in this project.

Step 6: Cardboard structure

I wanted, that final product would look nice. Therefore I decided to make handle from cardboard. Handle holds battery, switch, circuit and coil.

First, I made a sketch. There were no measurements. First I made three pieces that will end up a handle. Second task was to cut out openings for batteries and for switch. Then I glued handle together will wood glue and left it to dry for 12 hours (through the night). When glue has dried I punched a hole into section where switch will be. That hole is for wires to get through.

Last but not list thing to do was to glue coil to the handle. I have done that with help of hot glue.

Step 7: Put it together

Picture of Put it together
I made all components in previous steps. And now it’s time to put them all together. As first I glued in switch with hot glue, then I put in battery and at last I glued in PCB with hot glue. After that I made all the required connections and put metal detctor to the test!

Step 8: Conclusion

Picture of Conclusion
I put finished metal detector to the test:

This detector is really very simple one. But I must make a note that it is not meant for serious work. When I tested it outside, it didn't work propperly. But it is a simple and fun project for beginers. I must say I had a great time making it and using it!

I wish you good luck with making this metal detector and have fun while using it.
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lookaaz.4 days ago

hi, if i use normal inductor like the one in pic what is the range of detection ?
or it should be direct contact between the metal and the inductor ??

RaveenaK120 days ago

What could be the problem if the buzzer is producing sound even without placing any metal near to it? Can anyone help me out with this?

AbigailM11 month ago
BaadalB2 months ago

Hey!...Its me again. Can you suggest a way to make the metal detector louder?....Can I also add a small light bulb in the circuit so that it lights up when its passed over metal?

vonPongrac (author)  BaadalB2 months ago

Usually it helps if you put higher voltage on piezo element. Just try not to destroy the buzzer.

You could ad a small bulb but it will requaire some microcontroller processing. Lower in the comment section user arzedur did just that.

ffdqfg3 months ago

hi every one < can u help me

any project for gold detector i need this devices

BaadalB3 months ago

Ohk.....thanks!.....But I gotta make a VLF metal detector........do you have any website recommendations???

Or.............is a BFO metal detector better than a VLF one??

BaadalB3 months ago

Its a cool project, I want to make it too but what kind of metal detector is this? Is it a VLF, PI, or BFO metal detector?.....Please Reply ASAP! Thanks!

vonPongrac (author)  BaadalB3 months ago

It is close to BFO metal detector (but it is not one). It uses a oscillator and oscillators frequency changes with change of inductance. And that is all what is similar to BFO.

My simple metal detector is more proof of concept than a real deal....

rajvic775 months ago

cool diy project... I prepared everything except the inductor part.. Since I am new to winding the inductor, I have some doubts..

what is the thickness of the cardboard core of the inductor?

do I need to cover the winding using tape?

can overlapping of turns reduce the effect of inductance?

thanks in advance....

vonPongrac (author)  rajvic774 months ago

Cardboard do not efect inductance so it doesn't matter what thickness you are using. In fact any non magnetic or non conductive material will do the job. Also in my case cardboard is a way to mount coil on some kind of handle. You can make coil without any "core". Cardboard that I am using is about 5 mm thick.

You do not need to cover windings but make sure wire will not unwind on its own. So tape is dual purpose in my case: coil can not unwind itself and it looks kind of cool to me.

Overlapping can reduce inductance but effect is minimal. Just make sure you are using insolated wire and you can do few more loops.

sureshr14 months ago

thnk u

arzedur made it!1 year ago

this was easy :D

I converted the output signal into a TTL level. i programmed the arduino so that a few LEDs light up when a metal in the near of the coil.


hi.. do you have the arduino sketch for this??


arasradza arzedur4 months ago


any chance to get info about coil. could you share code for arduino, please.


vonPongrac (author)  arzedur1 year ago
Nice! :D
rajvic775 months ago

cool diy project... I prepared everything except the inductor part.. Since I am new to winding the inductor, I have some doubts..

what is the thickness of the cardboard core of the inductor?

do I need to cover the winding using tape?

can overlapping of turns reduce the effect of inductance?

thanks in advance....

rajvic775 months ago

cool diy project... I prepared everything except the inductor part.. Since I am new to winding the inductor, I have some doubts..

what is the thickness of the cardboard core of the inductor?

do I need to cover the winding using tape?

can overlapping of turns reduce the effect of inductance?

thanks in advance....

alireza19995 months ago
Hi.i have a quasion
the coil has 250 turns with 90mm width
so i need about 71 meters of transformer wire 0,2mm,right?
did you make the coil with about 71 meters of transformera wire?or im in wrong?
chetanp26 months ago

it is which type of metal detector vlf.PI or bfo

syeda.b.haque8 months ago

kindly upload a photo where soldering is shown.... also tell me is it 2.2microF capacitor 16V??

Manan19978 months ago

Can u please share a video of proper demonstration of the whole building process ?

FahmeedZ10 months ago

Can u tell me the detection range of this circuit?

magnific, please contac me to jonath55@hotmail.com

What's the rating of the buzzer?
skharel1 year ago

what will be the frequency while calculating inductance????

vonPongrac (author)  skharel1 year ago
One does not need frequency for calculating short cylindrical air coil inductance.

You can find formulas here.
vipfmz1 year ago

hi, if i want to use 0.3mm coil in the same diameter , hoe many turns i need to do ?


krm_priya1 year ago

i tried this project following the exact schematic.

It doesn't seem to work. I have checked the wiring thrice.

Can you please suggest me the possibilities where all it could have gone wrong?

Steph J1 year ago

Hi Mr vonPongrac . I like your project. Can u tell me how to do the coil in details pls? sorry I can't understand. and if we buy the 10mH inductor, is it need to put underneath the two cardboard? thank u so much.

vonPongrac (author)  Steph J1 year ago

In my case cardboard is only a bracket to mount coil on it. And it looks good. You can use 10 mH inductor as it is.

hi again.. how much is the DC current rating for the inductor and tolerance? Because I did bought the one that 10mA dc current rating and 10% tolerance but the sound of the speaker does not change.

vonPongrac (author)  Steph J1 year ago

I can't tell what are the ratings. It depends on wire gauge (resistance), frequency and coil inductance (I=U/Z, Z=R+jwL). I can measure resistance and inductance and I know what maximum voltage rating is. But I realy can not determine frequency (I should measure it but I don't own oscilloscope or frequency counter). I can guess that it is around 10 mA max like yours.

I do imagine that you bought yourself a inductor with core. It also depends on inductors core and how inductor is designed. With this aplication you should use inductor, that allows great dissipated magnetic field. Dissipated magnetic field is reason why this should work with cored inductors. In my case I only have main magnetic field (dissipatted magnetic field is almost infinitesimal) and greater area that magnetic field is covering. Because of that I should have greater frequency change.

All of stated above are only my predictions about this circuit. So reality can vary.

alright. Thank u so much for your help. :)

vonPongrac (author)  Steph J1 year ago

Also, in video provided in Intro, inductor is very small. I guess that it is similar to what you have bought. So it does work with small ready made inductors.

Check your connections and orientation of components one more time.

thnk u it was vry useful for us as v r doing this project.i have 2 questions.will the buzzer be continuously giving sound or only wen it is brought near the metal???can u list the things which this metal detector works???reply me fast!!!!

vonPongrac (author)  vidhya_rvkmr1 year ago

It will buzz all the time. Sound frequency should change when coil will be near metal object.
I tested it with nails, some tools that where on my bench, bike frame, on some metal shelfs. In terms of materials, it works best with steel.

Sir can I ask why is the buzzer continuously giving sound even if the metal is away from it? I just want to confirm it thank you

vonPongrac (author)  ashnernovilla1 year ago

It should buzz. When coil is near metal (or even strong magnetic field) sound should change.

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