Introduction: Simple Metal Detector

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.

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

Picture of 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.


jaswanthchakri (author)2017-09-12

What is 2μ2F capacitor?
Is it 2.2μF

robot1000 (author)2017-08-03

can we use any 8 pin ic except 555

Melwin Baby (author)2017-02-23

What is the vault of the capacitor

Use a 16V capacitor. The voltage on a cap refers to the maximum volts it can take before "popping". So seeing as the voltage source is 9V, anything above should be fine.

AsadB (author)2017-02-10

how much is the range?

T0BY (author)2016-12-05

I am very impressed!

Kevro669 (author)2016-09-20

Can anyone explain more about the coil? I have seen similar schematic with a bobbin inductor. whats the difference, if any?

vonPongrac (author)Kevro6692016-09-21

One could say that air coil used in my instructables is a bobbin inductor (wire wraped arround a cylinder).

Kevro669 (author)vonPongrac2016-10-18

Do you have a step by step of how you did the coil? Im in the process of building mine and im having issues.

Goldy851 (author)2016-09-17

what is 555?

FrankenPaper (author)2016-09-12

FYI: The link "web calculators for air coils" in Step 3 is 404.

vonPongrac (author)FrankenPaper2016-09-12

This instructables was made long ago... Things happen...

Problem resolved.

BenA93 (author)2016-09-08

Nice job, but could you edit this to say the 555 Timer. It is not a coil but an integrated circuit on a silicon chip. Call it the 555 IC so people will not be confused.

vonPongrac (author)BenA932016-09-08

Edited. Thanks.

MaurilioC (author)2016-09-01

Poderia ter utilizado um cartão mais fino, na parte inferior, previamente endurecida de cola de madeira. The closer to the metal coil, the more sensitive it becomes.

reshma234 (author)2016-02-18

What's the frequency range for the working?

reshma234 (author)2016-02-18

what's the frequency range for the working?

ShreyaC2 (author)2015-11-16

Can u please provide circuit diagram? For PCB?

mati ur rehman (author)2015-11-07

i want to make a metal detector using tda0161, when the detector detects the metal from a specific distance the buzzer sounds but as the metal comes near and near the buzzer sound increases!!

so anyone guide me for this

i want to use this with arduino

krm_priya (author)2014-05-28

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?

nancyjohns (author)krm_priya2015-10-27

maybe you could have added a non necessary capacitor for the speaker.

nancyjohns (author)2015-10-27

Very nice.

janbazh (author)2015-10-17

any body send me proposal of simple metal detector plz....... my email is

AbhishekT10 (author)2015-09-19

hiiii sir use this ckt bt its cannot work...

phalesh (author)2015-09-01

I want pcb layout
Any one can send the layout

wazab (author)2015-08-29

hey can i use a three leg capacitor

DhananjayG4 (author)2015-08-26

what is the diameter for the the cardboard used for coil?

lookaaz. (author)2015-07-25

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 ??

RaveenaK1 (author)2015-07-10

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?

AbigailM1 (author)2015-06-18

BaadalB (author)2015-05-26

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)BaadalB2015-05-27

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.

ffdqfg (author)2015-04-30

hi every one < can u help me

any project for gold detector i need this devices

BaadalB (author)2015-04-16

Ohk.....thanks!.....But I gotta make a VLF metal you have any website recommendations??? a BFO metal detector better than a VLF one??

BaadalB (author)2015-04-15

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)BaadalB2015-04-15

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....

rajvic77 (author)2015-02-17

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)rajvic772015-04-01

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.

sureshr1 (author)2015-04-01

thnk u

eswarasai veesam (author)2015-03-10

arzedur made it! (author)2014-07-01

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.

night.fury010 (author)arzedur2015-03-08

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


arasradza (author)arzedur2015-03-03


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


vonPongrac (author)arzedur2014-07-01

Nice! :D

rajvic77 (author)2015-02-17

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....

rajvic77 (author)2015-02-17

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....

alireza1999 (author)2015-02-09

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?

chetanp2 (author)2015-01-21

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

syeda.b.haque (author)2014-12-01

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

About This Instructable




Bio: I am an engineer and a maker who loves technology challenges.
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