G
goldjackal
First a quick bit of background. I live in Southern California, in the mojave desert area. I repair Radar Systems (which is like the big daddy of metal detectors) in the military, and I'm studying Electrical and Mechanical engineering.
A friends of mine here has been interested for quite some time in mines and gold detection. When he approached me recently about the possibility of building a metal detector, I wasn't really interested. But I guess I've been bitten by the bug. I have to be honest, while I have no real interest in getting rich from gold or anything like that, the ideas involved in this project have intrigued me. Greatly.
I've done a LOT of research over the past few weeks, and I'm going to go ahead on this project, though it's going to be a costly (He'll be paying for most of the project, which I estimate around $800) and long-term one for sure. The requirement is for search depths of up to several feet. It would be towed behind a 4wd vehicle in the desert. I know some of you probably consider driving a metal detector around to be cheating, but oh well
I'm just in the initial brainstorming stages right now, but I thought I'd share. I'll update as we progress.
Before I go further, the main technology I'm planning to use is VLF, though I may include PI and other modes someday. I want to start as simple as possible while still meeting the requirements. While PI systems are known to penetrate better for the most part, I like the better discrimination offered by a VLF system. (Maybe, if this really gets of the ground, run in PI most of the time, and switch to VLF when there's a hit, in order to verify the target is gold? Maybe.)
Antenna system: Because we want to cover a decent amount of ground at once, I'm sort of debating with myself over what to do. I've considered an array of receiving loops, but while dipole arrays are common in various applications, I've never really heard of an array of loops being used for anything, so I'll have to do more research on the viability of this. It would be nice, though, because then I could probably use monopulse to pinpoint location (in 2d). Otherwise, I've also considered having 2 large loops, XMT and RCV, of around 3' in diameter. I have concerns about sensitivity and noise, though. Until I figure out what SORT of antenna system to go with, I won't know the specific diameters/turns/gauge, etc. For frequency, I'm going to aim between 5 and 15 kHz.
Power: This is pretty important, but I haven't gotten there yet. Any suggestions? It depends a lot on the power needs of the design, and it's not very far along yet.
Trailer: The unit will be packaged inside a trailer of some sort, situated behind a 4 wheel drive vehicle. It will need to sit as low as possible without being damaged. I was thinking maybe a sled design of some sort, but it's just a thought right now. For the most part, it will be driven along washes out in the desert, so it should be pretty flat. The trailer will be wood/plastic/other materials than metal as much as is possible to avoid any interference. We will utilize foam heavily for damping and protection of components inside the trailer.
Processing: There will be a cable from the trailer into the cab of the vehicle, interfaced to a laptop (not included in my cost estimate), which will be the real brains of the operation. Most of the actual signal processing of the detector (sans some hardware amplifiers/filters 'n such) will be software based, utilizing the laptop. Also, all control (gain, noise floor detection, etc) would be via laptop. Such a system allows a lot of flexibility with display/alerts, upgrades, etc.
The laptop will also have GPS, in order to allow the ability to simply log a find and come back at a later time. If we really got crazy, we might also put up solar panels on the trailer. This is sunny SoCal after all.
Anyway, any suggestions? This might be a bit more ambitious than I have time for right now, but I'm already having fun just thinking about designing.
- Jack
A friends of mine here has been interested for quite some time in mines and gold detection. When he approached me recently about the possibility of building a metal detector, I wasn't really interested. But I guess I've been bitten by the bug. I have to be honest, while I have no real interest in getting rich from gold or anything like that, the ideas involved in this project have intrigued me. Greatly.
I've done a LOT of research over the past few weeks, and I'm going to go ahead on this project, though it's going to be a costly (He'll be paying for most of the project, which I estimate around $800) and long-term one for sure. The requirement is for search depths of up to several feet. It would be towed behind a 4wd vehicle in the desert. I know some of you probably consider driving a metal detector around to be cheating, but oh well
I'm just in the initial brainstorming stages right now, but I thought I'd share. I'll update as we progress.
Before I go further, the main technology I'm planning to use is VLF, though I may include PI and other modes someday. I want to start as simple as possible while still meeting the requirements. While PI systems are known to penetrate better for the most part, I like the better discrimination offered by a VLF system. (Maybe, if this really gets of the ground, run in PI most of the time, and switch to VLF when there's a hit, in order to verify the target is gold? Maybe.)
Antenna system: Because we want to cover a decent amount of ground at once, I'm sort of debating with myself over what to do. I've considered an array of receiving loops, but while dipole arrays are common in various applications, I've never really heard of an array of loops being used for anything, so I'll have to do more research on the viability of this. It would be nice, though, because then I could probably use monopulse to pinpoint location (in 2d). Otherwise, I've also considered having 2 large loops, XMT and RCV, of around 3' in diameter. I have concerns about sensitivity and noise, though. Until I figure out what SORT of antenna system to go with, I won't know the specific diameters/turns/gauge, etc. For frequency, I'm going to aim between 5 and 15 kHz.
Power: This is pretty important, but I haven't gotten there yet. Any suggestions? It depends a lot on the power needs of the design, and it's not very far along yet.
Trailer: The unit will be packaged inside a trailer of some sort, situated behind a 4 wheel drive vehicle. It will need to sit as low as possible without being damaged. I was thinking maybe a sled design of some sort, but it's just a thought right now. For the most part, it will be driven along washes out in the desert, so it should be pretty flat. The trailer will be wood/plastic/other materials than metal as much as is possible to avoid any interference. We will utilize foam heavily for damping and protection of components inside the trailer.
Processing: There will be a cable from the trailer into the cab of the vehicle, interfaced to a laptop (not included in my cost estimate), which will be the real brains of the operation. Most of the actual signal processing of the detector (sans some hardware amplifiers/filters 'n such) will be software based, utilizing the laptop. Also, all control (gain, noise floor detection, etc) would be via laptop. Such a system allows a lot of flexibility with display/alerts, upgrades, etc.
The laptop will also have GPS, in order to allow the ability to simply log a find and come back at a later time. If we really got crazy, we might also put up solar panels on the trailer. This is sunny SoCal after all.
Anyway, any suggestions? This might be a bit more ambitious than I have time for right now, but I'm already having fun just thinking about designing.
- Jack
