Metal Detector for University Project

[slmat27]

Good day everyone,

This is my first post in this forum, and I really want help from anyone. I have a project to do in my university to implement a mobile robot that detect mines in a mine-field. It is not a real mine-field nor real mines; the mines are metal cubes of dimensions 10 cm x 10 cm x 10 cm; and it will be buried under a sandy ground with maximum depth of 10 cm. The field is a rough terrain, so I must put the metal detector on the top of my robot so it will not hit the ground.

What I need is a metal detector; not the whole kit, just the sensor (I think it is called Search Coil). I will mount this sensor on my robot and connect it to my micro-controller. The required specifications are:
- Cost: about $100 or less
- Range of detection: 25 cm to 50 cm (most important)
- Weight: 2 kg maximum
- Size: none specified, I will take the available

I searched over Amazon to purchase one; however I could not find the range of detection in any of them. I need your help in either give me the range of detection for the search coils I found, or suggest me a better and suitable solution for my case.

Thanks in advance, and waiting for your reply...

Regards,

 

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[Bum Luck]

Interesting; a GPS equipped remote control detector. I wonder if it could leave a paint spot or flag or transmit coordinates where it got a hit. That would mean that we could cover a field while we're not actually there.

For your particular application, it would have to 'tune out' your robot. That would be tough. The only way I can figure to do it is to have the coil (light weight) extended away from the robot.

 

[slmat27]

Well, it is not Remote Controlled Robot - it is Autonomous Robot with GPS module and Compass.

And yes, the metal detector will be extended away from my robot. But I can balance it with another weight in the back, so it doesn't have to be very light weight search coil.

For now, I need to know the detection depth range for the metal detectors...

 

[slmat27]

Any help please...

What about the maximum detection range of depth of:
1. Fisher F2/F4 - 4" Search Coil

or

2. Bounty Hunter 8" Spider Search Coil

I found them at: http://www.kellycodetectors.com/accessories/searchcoils.htm

 

[Charlie P. (NY)]

Did they give you an indication of what metal the 10cm cube will be composed of?

As a rule of thumb a coil will detect t a depth of the maximun width. i.e. an 8" coil will detect to 8" deep. But that is based on silver dollar sized targets. A 10cm cube of brass woild be detectable 18" deep or much more by most dependable detectors. A steel 10cm cube, if using All Metal, should likewise trigger a response at 18" or better with most name brand detectors with a proper ground balance.

 

[slmat27]

The metal cube will be made from Stainless-Steel - which means I can use any of the available search coils.

Thank you Charlie

 

[Lakemonster]

Hmmm...

Unless your robot already has a metal detection circuit to plug the coil into.... you will need the control box for the detector as well as the search coil. The coil alone wont do anything.

Maybe Im not following what you are doing here.

 

[slmat27]

I don't have the metal detection circuit, but I have a micro-controller in which I can take any feedback signal and make my own circuit...

Question: when the search coil detect the presence of a metal in its range, it returns a voltage signal, right?

 

[Charlie P. (NY)]

Not that easy. A metaldetector generates a field with a transmitter and then interprets how the field reacts to the presence of conductive objects. The coil is just the transmit antenna surrounded by the receiving antenna. The circuitry in the unit housing is the transmitter and receiver and "brains" to interpret the eddy currents and field disruption within the influence of the search coil.

 

[slmat27]

hmm, I see

Can you link me to any website or paper where I can read more about that?

And in this case, what do I need beside the search coil?

Sorry for my many questions, but I am new in this area and I am using it just as a sensor

 

[woof!]

The searchcoil alone won't do you any good, you need the whole metal detector other than some of the mechanical pieces. To register detection in your system, you'll probably just take the audio signal from the phone jack of the metal detector. Whatever you plug into that circuit should provide a primarily resistive impedance in the range of 8 to 200 ohms in the audio range down to DC.

Most metal detectors are capable of detecting stainless steel that large and at that distance from the searchcoil, but the searchcoil has to be in motion preferably about 1 to 2 meters per second. Your robot is probably not going to be that fast, so detection depth will be considerably reduced.

--Dave J.

 

[slmat27]

What about the Hand-held Metal Detector similar to the ones used in Airports? (example: http://spy.manufacturer.globalsourc...metal/1051484609/Hand-held-Metel-Detector.htm)

I found that it's maximum range of detection is 20 cm, however, I guess if it uses the same concept of metal detectors of search coils, and I am searching for a Steel Metal Cube, then the range of detection will be more in my case, right?

Thanks again for you all...

 

[goldentruth]

I goin out on a limb here, but did you ever think a common music store might sell you a Guitar Pickup.
How about this magnetic pick up to be used as a sensor. (It's so silly, it just might work Pistacio!)
Good luck with that.

 

[woof!]

Simat, I think what you need to do is to get a real metal detector and play with it to see what it does.

The "airport" security wands aren't likely to be sensitive enough, get one designed for finding buried stuff. And, I recommend buying only a well known brand, and then only through a trusted dealer. There are a lot of poor quality units coming from China these days, including counterfeits of well-known brands.

--Dave J.

 

[goldentruth]

Opps! Thats Right, watch out for the Knock-offs!
( My oppinion: I like Made in the USA stuff.)

 

[Bum Luck]

I don't have the metal detection circuit, but I have a micro-controller in which I can take any feedback signal and make my own circuit...

Question: when the search coil detect the presence of a metal in its range, it returns a voltage signal, right?

That's not that simple. There's 40 years of technology in circuit design in a competitive industry, unless all you have to do is fool a lazy professor.

Not only that, a lot of mines are non-metallic.

 

[slmat27]

That's not that simple. There's 40 years of technology in circuit design in a competitive industry, unless all you have to do is fool a lazy professor.

Not only that, a lot of mines are non-metallic.

It is a course project, where we simulate a mine field and mines in the university campus. The mines are set to be a Steel Metallic Cube of 10x10x10 cm.

And what is important in this project is the Autonomous System of my robot and it's Path Planning in the mine-field - the metal detector is just a sensor here...

I need to get a metal detector, to detect the presence of a steel metal cube at a depth of 25 cm under ground. The metal detector should be operating with normal DC voltage (up to 24 volts); and when it detects a metal it returns an electric signal, either analog or digital, which I can manipulate using my micro-controller.