Presenting the NCSU (North Carolina State University) Underwater Metal Detector Kit: GitHub - crmorano/UWMD-NCSU: Underwater Metal Detector Design
This project is the results of a semester long senior design project intent on designing an inexpensive open source Pulsed Inductance Metal Detector that someone with basic soldering skills can put together relatively easily. One of the diving instructors at our university requested that our department try and figure this out so his scientific diving course could supply this kit to his students so they could have access to a metal detector on their dives.
When buying in batches of 5 (From SeeedStudio's Fusion PCB Service), the electronics cost less than $100. It uses a shield design to make assembly easier for users, so they don't have to try and solder down anything smaller than SOIC parts.
We do still need help, as there were 3 Electrical Engineers working on the project, and the project only lasted a semester, so there is no simple and easy waterproof chassis at the moment. Ours is built out of PVC (which we hope to keep in the design since its cheap and easy), and an electrical box (Mainly for ease of assembly). Hopefully, someone who has experience with Solidworks or similar 3D modeling experience can help come up with a chassis design as well as a new coil bobbin design to be 3D printed or otherwise easily manufactured.
As of right now it does work as a metal detector, but it only works on materials that react to magnetic fields. This is necessary to deal with the attenuation of electric fields in water. I am sure there are a ton of improvements to the device that can be made, however I've uploaded our functioning prototype's schematics and code.
We are still in the process of uploading files to Github, but I expect everything to be up there by the end of this weekend. Please take a moment to look over it if you are interested. And while I welcome suggestions, and even have a few for improvement, this project is not going to be a top priority for me to maintain. However, I will do what I can to make sure people can access the necessary files and upload updates as they come up with it.
One additional warning on the PCBs. They have been updated since our original design to reflect the necessary design changes for easier manufacturing. This means some of the parts have been moved around. I have not had a chance to order and test the board since I've done this (This involves my own personal cash). This means that I have possibly broken it somehow unintentionally. I was very careful, but it is a still an untested design.
Requirements for a case needs:
3 PushButtons of some form to use while underwater
1 Power switch (Currently a toggling push button) to use while underwater
A small clear display
Some easily resealable way to open up the case (Or a small section of it) to recharge the device on dry land/boat.
As of right now it does work as a metal detector, but it only works on materials that react to magnetic fields. This is necessary to deal with the attenuation of electric fields in water.
Did you mean to say that it only works on ferrous metals, not nonferrous? Nonferrous react to a magnetic field, too, just in a different way.
I'm very interested in seeing a schematic and finding out which kind of metal detection you are using.
Both the Eagle schematic and a PDF should be on the Github I linked above. If something is missing (I know the current assembly instructions are not there yet) or there is some difficultly, I'm still learning how to use Github, so just let me know.
We are used Pulsed Induction (Primarily by request of the diving instructor), and are basically primitively analyzing the changes in the inductance of the inductor based on things nearby. Its far from perfect, but it actually does work, though the range isn't amazing. Its also susceptible to 60Hz noise, which is a problem that needs solving. We have a simple passive notch filter that reduced it a little, but that part of the pcb layout is a little iffy.
I don't see any PDF or Eagle files, and the zip file only has an .ino file in it. Perhaps I don't understand how Github works.
Pulse induction is supposed to work well in conductive soil and seawater (being conductive), so a good choice for underwater. I'd heard they are good at picking up precious metals, which should mean they are good for nonferrous.
Its also susceptible to 60Hz noise, which is a problem that needs solving
There is probably not too much 60Hz EMI offshore at the bottom of the sea where you intend to use the device.
Yeah, and it still works onshore in our EE lab. It just occasionally needs recalibration due to the DC level of the measurement drifting up and down. And if you were feeling ambitious someone can design in an active filter to eliminate everything from probably 20Hz-1kHz with little issue to overall performance for dealing with the calibration.
We are still putting together the assembly instructions, however, we aren't exactly sure how to build a waterproof chassis, so that is open to debate if our instructions are useful.
While that definitely could work, I'm wondering if it isn't too expensive. It might still be the best option, but I can't figure out where to buy the housing and it looks like it alone is >$200 (US). There might not be a choice in this and it is somewhere to begin!
My hope is that the chassis won't cost more than $100, as the electronics, assuming you order 5-10 boards for a group of people from either SeeedStudio's Fusion or Itead Studio, cost around $80.
I am hoping that there could be a relatively cheap 3D printed design that could be coated/dipped in something to water proof it, that has flanged interfaces to PVC pipes, making it easy to seal and build with a clear plastic cover (Will Acrylic work?) and some form of reed switch as a button. This may be unfeasible for the actual waterproofing though. I am not a mechanical engineer or diver, so that's where I had this project off.
on the schematic for this detector in the TX side, there is a transistor but the part number is hard to make out because the diode label is blocking it.. Can you tell me the part number?
Most likely that is the IGBT, which I believe is Q1, so check the BOM for the part number. If I remember, I'll check the file tonight when I get home to double check, but I think the only transistor in that area is the IGBT. It is an STMicro part.
On the case, if I ever get around to maintaining it, I'll try to include some information on the Ikelite stuff, though I believe that is outside of the price range for the device. The hope is to keep it about the cost of an expensive textbook. However, I am an EE, so that may just be wishful thinking. With any luck, there will be another design project from the mechanical engineering department of my university to supply a housing.
If anyone wants to upload files, let me know how to give you access to the repository so you can do so.