Metal Detector

#3
Excuse me, Could somebody explain the theory of the metal detector circuit?
Could you be a bit more specific? What exactly would you like to know?

From what you've said, this is what I can tell you. The metal detector circuit, like its name, detects metal. This happens when a piece of metal is brought close to the inductor or "choke". A piece of metal will change the circuit's choke frequency which causes the 8 0hm speaker to emit a sound.
 
#4
I've updated my breadboard layout


I also made a Microsoft word document that contains both the circuit diagram and the breadboard layout in a neat, one page, file that is ready to print. This file is availbe online and you can download that here.
 
#6
what software do you use for the breadboard???

I use a free program called Paint.NET that you can download online. The program is for making or editing pictures so you can't actually test anything in the program itself. The testing phase needs to take place on a breadboard itself.
 
#8
hey... i"m not able to find an inductor of a such value.... so plz help me if the problem perexist, that other value i can use. and which other component to change????
plz its urgent...
 
#9
hey... i"m not able to find an inductor of a such value.... so plz help me if the problem perexist, that other value i can use. and which other component to change????
plz its urgent...
I'm sorry I couldn't get to your post sooner. I haven't checked my e-mail in awhile.

Click on this link to get the exact same inductor used in this video. As you can see in the comments, I had asked the uploader which inductor he had used he gave me that link. So it's safe to say the circuit will work with this one. I'm also going to include the Breadboard Layout that was used in that video.

Could you post your results here along with your bread board once you've built it?
 
Last edited:
#11
Hey Justin, I've Choosen This Circuit As My Final Secondary School Project. Practically It Is Workin' But In Really, I've No Idea On The its WORKING OPERATION (i.e: how the circuit works.).
so if possible, plz give me some.
BEST REGARDS!!!
 
#12
Hey Justin, I've Choosen This Circuit As My Final Secondary School Project. Practically It Is Workin' But In Really, I've No Idea On The its WORKING OPERATION (i.e: how the circuit works.).
so if possible, plz give me some.
BEST REGARDS!!!
You got it working? Nice! Could you post some screenshots and/or show us a video? I like seeing other people's work.

I've said this in another post but I'll do it again since I learned some more stuff in physics. When the metal gets close to the inductor, it causes electrons in the copper coil to move, which creates a change in current and creates a tone in the speaker. I may be wrong, but this is my best educated guess that I can give. If somebody else knows more than me, feel free to help this lad out.
 
#13
You are correct Justin. When an inductor gets near a metal object it induces a current into the object and then that object will change the current in the inductor, basically. I have a link to a YouTube video here from a guy that does some really great electronic learning videos. Although this video does not specifically talk about metal detectors I think all of you will enjoy it and find this guy to be a great teacher on YouTube.

 
#14
hello everybody!! guyz i'm sorry, i've many questions but i've to know all about this circuit.... i would like to ask, can please someone tell me the function of each component in da circuit?? and if possible what will happen if taken out?
...thank you... i'm really in need of help.
 
#16
Well I'm not sure what every component in the entire circuit does. The only reason why I assume you would ask such a thing is because this is a school assignment or something of the sort. However, I can tell you what I do know
  • Inductor: When the metal gets close to the inductor, it causes electrons in the copper coil to move, which creates a change in current and creates a tone in the speaker. Without this, the speaker wouldn't turn on only when metal is close.
  • Speaker: Produces a tone to notify the user that metal is nearby. Without this, the circuit could work just fine but the user would have no idea when metal is close. It could easily be replaced with an LED or buzzer.
  • Resistor: I'm guessing it's there to just provide a current for something. What for? I'm not too sure.
  • Capacitors: Your guess is as good as mine
 
#17
hello every body! could plz someone tell me what to do, i've implemented this circuit but it generate a sound even when there is no metal material to be detected... but when i approach a magnet or metal material it changes the sound! plz someone to advise me what to do so that the occurred noise be removed
-regards!!!-
i'm also working on this circuit report... maybe in one week or less i will upload it.
 
#19
hello every body, can somebody plz tell me how to calculate the detection limitation of the circuit? (i.e: area inwhich it will detect?)
I have never built a metal detector and really can't answer your question but I did find this web site that looks like it could be very helpful to you. Good luck! EDIT - After reading the web site a little more it may not be that great. Best bet is to search for building a metal detector, I am sure you will find more information that way if no one here answers your question.

http://www.wikihow.com/Build-a-Metal-Detector
 
Last edited:
#20
hello everyone I done this project and it works now i need explanation about the capacitors why the sound change if i change the value of capacitor i know it but i can't elaborate clearly it on my mind .. sorry in my grammar hehe