Introduction: Simple Metal Detector

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

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

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

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.