How to Make a Metal Detector

I had to get riddle of the bubbles. for science. Here’s how you use it. Hold the trigger to scan, point at some metal,and the pitch changes. Now in this unit, there was a fancy motor with spinny lights that I wanted to keep intact. So I decided, if you struck gold, then it’ll give you a damn good lights how. It’s just a Blackberry. So here’s how it all works.

When you connect a capacitor and an inductor together, AKA an LC circuit, they start charging each other back and forth, creating an oscillating current. Now, if we use a really big coil, we can change the inductance of the coil by changing the permeability of the air around it. The change in inductance will change the frequency  of oscillation. And this is what happens, when metal comes close to it. Now, if these components were perfect, they would charge each other forever and ever. But they aren’t. So in reality, our oscillation actually dies down.

To fix that, we’re going to add a single transistor amplifier to create a feedback loop in the LC circuit. Now this whole thing, is called the Colpitts  oscillator. And with that, we now have a steady, usable oscillation. But! It’s not over. The frequency of oscillation is in the 100kHzrange, which means it’s nothing that we can hear.

So what do we do about that? Arduino to the rescue! We’re going to feed the oscillation into a counter. And when the trigger’s pressed, the Arduino program will translate that oscillation into an audible tone, that gets played out the speaker.And just for fun, when our oscillation exceeds a certain threshold, we’re going to turn on our light show, because. why not? We’re also going to add a dial on the side to adjust the sensitivity.

And we’ll use this button to set the best one. We’ll look at the schematics at the end of the video. But for now, let’s build stuff! Okay! First thing we have to do is embed a coil into the base. Take a spool, take some wire, give it 50 wraps or so, then we cut a hole into the base and drop in a spool. Done! Now let’s open the housing and see what we got. Not going to need that circuit board anymore,so. get out of here! We’re replacing the circuit with our own circuit board. There’s nothing on here. Oh right! Let’s put our oscillator in place.

Just like that. There we go! Now let’s go over to the Arduino and upload some code to it. Then lift off the chip with our code and embe dinto the circuit board. Like this! Now let’s go over to the junk pile, salvage another transistor to drive the speaker, and salvage a mosfet to drive the motor. Add them to the circuit board as well, and now, it is ready my lord. Back to our good metal detector! There wasn’t a dial here to begin with, but that’s okay. We’ll just blow a hole on the side and add one ourselves. Let’s plug everything into our shfancy new circuit board. Pop in some batteries, and give it a test.

Hey, if you’re interested in building one of these things for yourself, then here’s the full schematics I used for this project. A link to this and the Arduino code can be found in the description box. And for those who are interested in the technical details that didn’t get to make it in this video. Fear not! I’ll be writing an article for this project,so stay tuned! You can follow me on Instagram, Twitter, Facebook,and I’ll update you when that comes out. If you want to see more things get the Arduino upgrade, then check out some of my other projects. Or you can subscribe to the channel.

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