Metal detector schematic?  - Page 1
Forum section: electronics / projects

author: cdev
author_rank: Super Contributor
timestamp: May 19, 2022, 01:13:46 am
content: I'm looking for a way to build a semi-decent metal detector myself, I don't know how much I'll use it or if I will but its something I would like to have.I see a lot of new and used ones online. But I dont want to spend much. If possible. I like winding coils, etc. I have a nice darsonval meter movement that I could use, (center reading)I really don't know if it needs a center or side reading meter, I have a lot of parts, which I like using. So I am looking for interesting electromagnetic projects.Could I (legally) use RF to peer into the ground? Now that would be interesting!

author: ledtester
author_rank: Super Contributor
timestamp: May 19, 2022, 01:29:52 am
content: You might find DiodeGoneWild's two videos detailing his experience building one from scratch interesting/informative:DIY DD metal detector 1 - first successhttps://youtu.be/eCRgNr6jj2gDIY DD metal detector 2 - coin at 35cm, audio indicator, PCBhttps://youtu.be/-czOV-hKSlA

author: pqass
author_rank: Super Contributor
timestamp: May 19, 2022, 01:33:32 am
content: See here for the first of two parts (schematic at 5:20):

author: themadhippy
author_rank: Super Contributor
timestamp: May 19, 2022, 01:37:52 am
content: https://worldradiohistory.com/UK/Practical-Electronics/00s/Everyday-Practical-Electronics-2002-10.pdfhttps://worldradiohistory.com/UK/Everyday-Electronics/70s/Everyday-Electronics-1972-05-S-OCR.pdf

author: tepalia02
author_rank: Regular Contributor
timestamp: May 19, 2022, 07:26:37 am
content: I once used Arduino UNO and metal-touch sensor for this project.https://sensorkit.joy-it.net/en/sensors/ky-036

author: Gyro
author_rank: Super Contributor
timestamp: May 19, 2022, 09:06:10 am
content: Quote from: themadhippy on May 19, 2022, 01:37:52 amFor some reason, I remember being fascinated by the coil construcion and adjustment details of the 2002 one. It's one of those articles that are very well written.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: May 19, 2022, 01:12:57 pm
content: This article is very old, in fact it uses tubes. Valves for some! I'm not suggesting it as a project, just as educational material. What's interesting is the design of the transmit and receive coils to get a large baseline. Metal detectors don't go much deeper than the diameter of the coils, so I'm guessing this might do better. Naturally one would want to update it to solid state circuits. It might also not be legal these days.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 19, 2022, 01:32:33 pm
content: There are different was the metal detector work. I know of 4 types:1) The target changes the resonance frequency of an LC resonator - so detection of frequency change2) The target changes the coupling between 2 coils or set of coils - detected is the amplitudeThe coils could be at an angle or a round and figure 8 coil, so that in free space there is no coupling.3) Pulsed operation and detection of the delayed part of the decay if the magnetif field4) measurement of the effect on the earths magnetic field, so just a magnetic field probe. This system can go relatively deep, but only detects iron/steel.

author: Gyro
author_rank: Super Contributor
timestamp: May 19, 2022, 05:54:18 pm
content: 4.1) Proton Magnetometer...https://worldradiohistory.com/UK/Practical-Electronics/70s/Practical-Electronics-1970-10.pdf

author: RoGeorge
author_rank: Super Contributor
timestamp: May 19, 2022, 06:14:30 pm
content: Quote from: cdev on May 19, 2022, 01:13:46 amDepends on where you live. Here in Romania it is illegal to use metal detectors (not an EU law, it was illegal even before Romania joined EU). Not sure if owning one without using is legal here, probably not.

author: Gyro
author_rank: Super Contributor
timestamp: May 19, 2022, 06:28:02 pm
content: That's an odd law, I wonder whan the historical basis of that is.In terms of using RF to peer into the ground, I think that comes under the heading of 'ground penetrating radar'. I don't know what the licencing and power restrictions are, but they are capable of mapping changes of ground density and material changes, revealing archiological features. I'm not sure whether you would get sufficient resolution forsmallmetalic items [Edit: Ah, maybe, depending on frequency].https://www.groundpenetratingradar.co.uk/about/how-does-gpr-work/https://en.wikipedia.org/wiki/Ground-penetrating_radar

author: MK14
author_rank: Super Contributor
timestamp: May 19, 2022, 06:41:11 pm
content: Quote from: RoGeorge on May 19, 2022, 06:14:30 pmThis website, doesn't seem to agree with you:https://detectingschool.com/metal-detecting-in-romania/Quote

author: RoGeorge
author_rank: Super Contributor
timestamp: May 19, 2022, 06:56:30 pm
content: I remember them differently, but I might be wrong.Glad to hear they are lighter.Later edit:--------------I've just checked. You need a permit to buy/own a metal detector, no matter where you want to use it.And if you use it in an area considered archeological site, registered detector or not, straight to jail!Ordinul Nr. 251/409/2275/M 115 din 31 mai 2004https://legislatie.just.ro/Public/DetaliiDocumentAfis/54142

author: n5al
author_rank: Contributor
timestamp: May 21, 2022, 11:36:03 pm
content: I don't know how accurate the list is, as laws are always changing, but this guy has made a big effort to document metal detecting legality on a country-by-country basis:https://md-hunter.com/list-of-countries-where-metal-detecting-is-allowedbanned/And just for fun...Our forum members from Canada might remember this comedy skit, from a TV episode of "TheRedGreenShow".

author: antenna
author_rank: Frequent Contributor
timestamp: May 23, 2022, 02:26:54 am
content: Here are two metal detector schematics from a book (Encyclopedia of Electronic Circuits) I mailed home from a minimum security prison that was salvaged from a dumpster behind a library while doing community work. The book was originally bought by a ham (SK) in 1985 when the book came outUnfortunately, he passed at about the same time as I retrieved this book from the dumpster, so I can only assume the family had donated his books and the library sent them straight to the trash. I'm glad I was able to rescue this one.