Sensitive STAMP based Metal Detector - enjoy!!
Beau Schwabe
Posts: 6,563
I know that this subject comes up every now and then about someone wanting to build a Metal Detector.
....So today was a good rainy day, and I decided to do a little testing with this idea in the back of my mind.
This design can be scaled and equipped with multiple "sense" coils, that should be able to compete with some
of the best Metal Detectors out there.... This is a unique implementation of the popular PI (Pulse Induction)
Metal detector that provides a STAMP RCTIME range of approximately 30000, on the original BS2 platform,
from "no metal" to "all metal".
Have Fun!!
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Beau Schwabe - Mask Designer III
National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071
Post Edited (Beau Schwabe) : 9/4/2004 4:56:24 PM GMT
....So today was a good rainy day, and I decided to do a little testing with this idea in the back of my mind.
This design can be scaled and equipped with multiple "sense" coils, that should be able to compete with some
of the best Metal Detectors out there.... This is a unique implementation of the popular PI (Pulse Induction)
Metal detector that provides a STAMP RCTIME range of approximately 30000, on the original BS2 platform,
from "no metal" to "all metal".
Have Fun!!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe - Mask Designer III
National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071
Post Edited (Beau Schwabe) : 9/4/2004 4:56:24 PM GMT
1155 x 887 - 29K
1159 x 756 - 22K
1024 x 683 - 131K
1024 x 683 - 59K
Comments
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"OIOOIOOO OIIOOIOI OIIOIIOO OIIOIIOO OIIOIIII OOIOOOOO OIIIOIII OIIOIIII OIIIOOIO OIIOIIOO OIIOOIOO OOIOOOOI"
·· Could you post some pictures of the coils, and perhaps how they are arranged?· While you provided some nice schematics, a look at how things should go together would be nice, if it's not too much trouble (read: you already buried it).
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Chris Savage
Parallax Tech Support
Post Edited (Chris Savage (Parallax)) : 1/22/2008 3:55:25 PM GMT
It's not quite buried, however it might be awhile on the pictures.... (read: My wife is out of town with the digital camera).
The coil layout is pretty much like the design notes... except taped on the bench right now - grin. looks sorta like a bio-hazard
symbol with the three coils at 120 deg to each other (flat-2D)
I will post pictures when available.....stay tuned.
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Beau Schwabe - Mask Designer III
National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071
Did you wind the coils yourself?· Was wondering if you got dimensions and all...
Thanks
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·
Steve
http://members.rogers.com/steve.brady
http://www.geocities.com/paulsopenstage
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
Yes, I did wind the coils myself...If you look at "Metal Detector - NOTES.gif" you will see a description
of how the coils are constructed as well as the calibration method I used to get this thing going. I used an empty
film canister, which turns out to be about 1 and a quarter inch diameter, as the form for winding the coils.
The important thing to remember is that the ACTIVE coil and the SENSE coil have the same characteristics and
even this isn't absolutely written in stone. The Coils can certainly be larger or smaller diameters depending on
your application needs. Feel free to experiment with different coil shapes, sizes etc....They don't necessarily
need to be round... they could be square or even triangle. A good test setup would be to have various coils that
are binary weighted... what I mean is for example one set of coils might have 50 total turns, the next 100, 200,
400 etc. Try intermixing them to see how your results vary. I might point out that a scope really helps in a
project like this especially since the oscillator circuit runs at about 750kHz with the project notes that I provided.
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Beau Schwabe - Mask Designer III
National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071
Post Edited (Beau Schwabe) : 8/31/2004 6:42:32 AM GMT
Thanks Beau!
Thank you! Sounds like you are volunteering...
Honestly, I think people are just afraid to wind their own coils.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
I might have made som silly beginners mistakes, but the inability to calculate the design is most frustrating. Could you please provide some of the formulas you used while designing the circuits?
I will send you some pictures of the progress and practical use if I succeed...
What have you put together so far, and where are you having problems with the calculations?
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Now I would like to increase the range of it, how do i balance the circuit for larger coils?
Jonasd
How much larger coils? ... The balancing should be about the same... I noticed with the adjustment coil that you had two separate wires going to gnd... this coil should be a closed loop "shorted" with a single wire going to ground.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Yep that was a silly one ....·How much larger? Well range is the criteria of optimization so let's say a clear identification of a·small coin·at about 5 inches (in the ground). I found some formulas for·inductance for single layer air coil, is it a reasonable approximation to regard the coil as single layer?
Jonasd