Metal Detector Beginning Hep

Thread Starter

Grizzly09

Joined Oct 24, 2017
11
Hello everyone
I'm beginning to make metal detector.
23476865_795790733942593_2078673356_n.jpg
What do you think about this circiut and i can't quite understand.
Any help will be helpful.
Thank you
 

philba

Joined Aug 17, 2017
960
What do you think about this circiut
Not much as it clearly isn't a metal detector. You'll need a search coil to start with, not an off the shelf inductor.

Google-fu will yield you hundreds of circuits. I'd start with a very simple design.

This page is a good starting point. I'd build a frequency shift detector to start with. If you want to go farther, a pulse induction detector is considerably more capable.
 
Last edited:

ian field

Joined Oct 27, 2012
6,539
Not much as it clearly isn't a metal detector. You'll need a search coil to start with, not an off the shelf inductor.

Google-fu will yield you hundreds of circuits. I'd start with a very simple design.

This page is a good starting point. I'd build a frequency shift detector to start with. If you want to go farther, a pulse induction detector is considerably more capable.
The simplest is nothing more than an oscillator used in conjunction with a pocket transistor radio - I forget what you tune the oscillator to beat with, but the oscillator tank coil is also the search coil - conductive objects interfere with its inductance and shift the oscillator. Heterodyne whistles indicate a winner.
 

Dodgydave

Joined Jun 22, 2012
10,050
Hello everyone
I'm beginning to make metal detector.
View attachment 139063
What do you think about this circiut and i can't quite understand.
Any help will be helpful.
Thank you
There are two main designs, The Bfo type,
http://www.zen22142.zen.co.uk/Circuits/Testgear/bbmd.htm


or the Induction Balanced...the easiest one is Induction balanced as it uses one detect coil.

https://www.google.co.uk/amp/www.instructables.com/id/Simple-metal-detector/?amp_page=true

Plenty of circuits here,
http://www.discovercircuits.com/S/s-metal.htm
 
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shortbus

Joined Sep 30, 2009
8,820
But to me this is another one of those things that an off the shelf professional model will in the end be cheaper. Especially when the OP says, "What do you think about this circiut and i can't quite understand."
 

ian field

Joined Oct 27, 2012
6,539
But to me this is another one of those things that an off the shelf professional model will in the end be cheaper. Especially when the OP says, "What do you think about this circiut and i can't quite understand."
Radio projects hardly ever get offered to beginners these days - metal detector projects probably moved up a place.

There's a lot of ways to skin this particular cat, some barely more difficult than a basic regen radio.
 

philba

Joined Aug 17, 2017
960
There are two main designs, The Bfo type,
http://www.zen22142.zen.co.uk/Circuits/Testgear/bbmd.htm


or the Induction Balanced...the easiest one is Induction balanced as it uses one detect coil.

https://www.google.co.uk/amp/www.instructables.com/id/Simple-metal-detector/?amp_page=true

Plenty of circuits here,
http://www.discovercircuits.com/S/s-metal.htm
Actually, there is a third kind, pulse induction ,shown in the link I posted way back towards the top this post.. It's more complex when built with logic but is more sensitive. It works similar to sonar in that it pulses the search loop and then "listens" for the induced field decay. Slower decay means something's there. I've been looking at adapting one of the designs to use a microcontroller to replace all the logic and timing generation. Could wind up being relatively simple. Gotta fix my scope first, though.
 

joeyd999

Joined Jun 6, 2011
4,477
Lol. That cracks me up. It can detect a coin if you hold it to the inductor.
It's a concept design -- and I like the author's concept.

If I wanted to, I'm sure I could design one that would perform as well as all but the most expensive metal detectors.
 

philba

Joined Aug 17, 2017
960
The trick is to make a search coil that works. I agree that it's interesting in it's minimal design. Don't know how effective it will be.
 

philba

Joined Aug 17, 2017
960
Some people code PICs to emulate the 555 timer.......................
ATTiny's too.

It may seem crazy but there is no cost advantage to using a 555 over a low end micro. There are a huge number of choices for less than $0.75. When you add in the other components to make the timer circuit, it's pretty much a wash. Maybe even cheaper for longer timings.

Plus, you can "emulate" multiple 555s in a single micro and all sorts of combinational logic. And you get the ability to make timing changes without changing the hardware. When I realized that many years ago, it was a "game over" moment for me.
 
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