# 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

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

## Step 2: 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

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

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

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

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

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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## 109 Discussions

I have a lot of questions for this as I have no experience at all with these things. I doubt I will get a reply from the author but it would be highly appreciated. I just need this thing to work for my school project. It's makes up 6 marks of my final grade. I'm desperate. ANYONE WHO CAN HELP, PLEASE HELP!

1. I am using a buzzer. Everything has already been soldered (idk if its correctly done, more on this later) and on testing, there is no noise at all from the buzzer. All parts are exactly the same, and the buzzer is 3V DC. What voltage should the buzzer be for 9V battery.

2.I had a really hard time soldering the wires to the 555 because of its tiny size. The solders are somewhat overlapping (as, two tips of the 555 have soldering between them) and I guess this is one of the reasons it is not working. Is there a way to make life easier for soldering like using a 555 socket? Will that help with increasing the distance between the tips to make things easier to solder?

3. The coil I made is was with 50 m of copper wire. I couldn't buy more as it is 50 cents a meter where i live. 100 m would have cost me \$50. I am not sure about how many turns I made and I did lower the width of the coil to try and compensate for the less wire. (idk what I'm doing). I'm guessing that the inductance is nowhere close to 10mH. I'm thinking of buying an already made inductor but its tiny and looks like a capacitor. How would that be used to detect a metal? No idea

Lastly,
4. What kind of wire do I get? I got the type with the insulation around multiple thin wires. And two such wire are stuck together. Black and red insulation with multiple wires in the WIRE. So.. should I just get the type with single wires or just make do with the ones I have?

Please help me. Anyone. Just tell me. I have 3 weeks from now to make this properly and submit it.

Hi - This will be too late for your project, but if somebody else sees this:
You want to use magnet wire - that is, very thin single strand copper wire with just a thin layer of lacquer as an insulation. Look at the picture for step 3 - the proper wire about the thickness of hair.
If everything else fails, you can also use the wire from the coil of a speaker -
And no, you cannot use the ready-made inductors. Most of these are build to be used as electronic components, and they are small to fit on circuit boards. A metal detector works by bringing some conductive material into the inside of a coil and changing the characteristics of the coil in the process - the coil of a metal detector is large so that you can test a larger area

I tried this out but the buzzer just buzzes like crazy all the time. Any Solutions?

that's wonderful tips

can we use any 8 pin ic except 555

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.

how much is the range?

I am very impressed!

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

2 replies

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

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

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

Problem resolved.