Instructables
Picture of Simple metal detector
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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
Parts:
- 555
- 47 kΩ resistor
- two 2μ2 F capacitor
- PCB
- 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).

Tools:
- 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

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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
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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.
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FahmeedZ5 days ago

Can u tell me the detection range of this circuit?

magnific, please contac me to jonath55@hotmail.com

Amiel Garcia2 months ago
What's the rating of the buzzer?
skharel2 months ago

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

vonPongrac (author)  skharel2 months ago
One does not need frequency for calculating short cylindrical air coil inductance.

You can find formulas here.
arzedur made it!2 months 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.

Unbenannt.PNG
vonPongrac (author)  arzedur2 months ago
Nice! :D
vipfmz3 months ago

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

thanks...

krm_priya3 months 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 J6 months 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 J5 months 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 J4 months 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 J4 months 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.

vidhya_rvkmr7 months ago

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_rvkmr5 months 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.

ashnernovilla7 months ago

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)  ashnernovilla5 months ago

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

sri charitha7 months ago

hii sir... i used a 10mH inductor instead of the coil...i am getting a continuous buzzer sound as soon as giving a supply of 9v...why is it happening?plz can you reply me fast...i need it for my school project?

vonPongrac (author)  sri charitha5 months ago

It should give continuous sound. When coil is near metal object, sound frequency changes.

jahanzeb2006 months ago

sir, what type of gauge wire you used in this metal detector project?

vonPongrac (author)  jahanzeb2005 months ago

I belive it is 23 or 24 (0,25 mm^2). You can use anyone you like or have. Just be sure to use online calculator since number of turns will change.

jhunix036 months ago

can it detect gold?how man inches it could detect something pls anwer fast thanks!

vonPongrac (author)  jhunix035 months ago

It does not go deep, maybe inch (2 cm). I did not tested it for gold but in theory in best case it should detect gold very porly, since gold is very good conductor. But I doubt it (performance is so bad)!

lorgenson5 months ago

i realy like it

vonPongrac (author)  lorgenson5 months ago

Thanks!

Prabhu98 months ago

I like the way it's made, but where did you connect the wires from the coil to?

vonPongrac (author)  Prabhu98 months ago

In Step 3 (Coil) you can see that there are some scrap wires connected to the copper wires. Then in Step 5 you can see that those scrap wires are connected to the circuit. In Step 2 you can see where you connect coil into circuit (uper left element).

rimar200012 months ago
Thanks for sharing.

I have a question maybe you can answer: what impact does the captor coil diameter on detector performance? More sensitivity? More insight? None?
vonPongrac (author)  rimar200012 months ago
Capacitor and coil creates oscilator. Both values (capacitance and inductance) impact to the frequency. So if those coils have different diameter and the same inductance, I do belive that there will be no difference in performance. But you must know that with certain diameter coil's magnetic field will be very week and it won't work propperly. You can make difference with magnetic core. I do belive that coil with magnetic core can be smaller for same results and detector can even perform better. The only thing that you get from smaller diameter is more insight, but it is not very significant.

Let me remind you that this circuit is not for any serious work. It is good for finding nails and other metal object if you drop them. But for nothing else.
What about,detecting No ferrous metals, as cupper
vonPongrac (author)  Dardaro8 months ago
I tried it out, but it doesnt seem to work.
Thanks for your reponse, I will take it in account.
YipAvenger8 months ago
How do you arrange the wires?
sonkaraman10 months ago
can u please provide a simplified circuit diagram the ones available on the internet does not work
vonPongrac (author)  sonkaraman10 months ago
There is no other schematic. The one I posted in Step 2 work just fine.
ok so do we have to connect pin 5 to anything?? and what about pin 7??
vonPongrac (author)  sonkaraman10 months ago
Pin 5 is NC (not connected). Pin 7 also is NC. As in schematic. You can also try circuit from two comments above. I did try it but it did not work. Try it and please let me know if it works.
mohitey00710 months ago
Can u check this circuit on link http://www.555-timer-circuits.com/metal-detector.html
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