How to Make a Metal Detector: Step-by-Step Guide

Published: 14 Oct 2024

A metal detector is a device used to detect metal objects. Making a metal detector using a coil is a little bit tricky, but it is still fun and will also enhance your knowledge. Although, a calculator and radio metal detector can be easier to make. But by creating an electromagnetic field with a coil of wire and other basic electronics, you can make a more sensitive and effective detector. This article will provide step-by-step guidance about how to make a metal detector easily and practically.

Table of Content

Materials You Need
How It Works
Step-by-Step Guide
Troubleshooting Tips:
Final Words

Materials You Need

Search Coil (Copper Wire): This is the most important part of your metal detector. You will need about 20-30 feet of insulated copper wire (20-24 gauge).
Battery (9V): To power the circuit.
Buzzer or Speaker: This will create the sound when metal is detected.
Resistors and Capacitors: Basic electronic components used to manage the current in the circuit. You’ll need a few small resistors (1kΩ to 10kΩ) and capacitors (between 100nF and 1µF).
Transistor: This is used to amplify the signal when metal is detected. A common transistor like the BC547 will work.
Switch: To turn the detector on and off.
Soldering Iron and Solder: This is used to connect the electronic components.
Plastic Disc or Circular Object: Wrap the wire around and make the coil (e.g., a lid or piece of cardboard).
Wires: For connecting the various components.
Breadboard or PCB (optional): To assemble your circuit without soldering.

How It Works

When the current passes through the coil, it creates an electromagnetic field. When this coil gets close to another metal object, it causes a disturbance in the electromagnetic field, which changes the electrical current flowing through the circuit. The detector detects this change and sends a signal to the buzzer or speaker, that lets you know that metal is nearby.

Step-by-Step Guide

Step 1: Make the Search Coil

The first thing you need to do is to take a copper wire and wrap it around a circular object (like a plastic lid or piece of cardboard) to form a coil. You should make 20-30 loops of wire. The coil size must be around 6 to 12 inches in diameter.
Moreover, you should leave enough wire at both ends so you can connect the coil to the rest of the circuit later.

Step 2: Build the Basic Circuit

At its core, the circuit consists of:
1. Battery to power the circuit.
2. Transistor to amplify the signal.
3. Resistors and capacitors to control the flow of electricity.
4. Buzzer or speaker to make a sound when metal is detected.
You can either use a breadboard to quickly build the circuit without soldering, or you can solder the parts directly onto a PCB (Printed Circuit Board).

Step 3: Connect the Coil to the Circuit

Now, you need to connect the two ends of the copper coil you made earlier to the circuit. The coil acts as the “sensor” of your metal detector.
Connect one end to the base of the transistor (this controls the transistor), and the other end to the power supply (battery).

Step 4: Attach the Buzzer or Speaker

Furthermore, you need to connect the buzzer or speaker to the output of your circuit. This is what will make the sound when metal is detected.

Step 5: Add the Power Supply

It’s time now to connect your 9V battery to the circuit. You should use a switch so you can turn your metal detector on and off easily.
Make sure you connect the battery correctly, with the positive (+) side going to the power input of the circuit and the negative (−) side going to the ground.

Step 6: Test the Metal Detector

Once everything is connected, turn on the switch and test your metal detector by bringing it close to a small metal object, like a coin or nail.

Step 7: Mount the Coil and Circuit

After testing, you can mount the coil at the end of a broomstick or long handle, like on a professional metal detector. This will make it easier to use.
Tape or attach the coil securely at the end of the handle, and keep the circuit in a small box or housing to protect it.

Troubleshooting Tips:

No Sound: If the buzzer doesn’t make any sound when you take it close to any other metal, check all the connections carefully. Make sure the battery is connected correctly and the transistor is working.
False Alarms: If the buzzer keeps going off, even when no metal is nearby, try adjusting the coil size or re-check the placement of resistors and capacitors in the circuit.

Final Words

Building a metal detector using a coil, some basic electronics, and a little patience is a great way to learn about circuits and electromagnetic fields. While this homemade version may not be as powerful as commercial metal detectors, it’s a fun project that teaches you the principles behind these fascinating devices. You can use it to search for small metal objects like coins, nails, or even small pieces of jewelry!

Happy hunting!