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Beach Detecting Rover project

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  • #16
    Instead of GPS you could always use triangulation. Simply use 3 stationary antennas and use signal delays to determine better location coordinates. Civilian GPS will get better in the next couple of years, but will never be good enough for this type of application.

    Yes, this is what I would propose.

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    • #17
      Thumbs up already implemented.

      Originally posted by Farside View Post
      Great idea Tinkerer!

      Can we have the "like or "thumbs up" feature activated please moderator? :-)
      You can already add a "thumbs up" icon to your reply, as I have done here.

      Look for the Post Icons below your reply.

      Comment


      • #18
        OK. I've been looking at the metal detector portion of the rover, and I'd like to get some input. I've ordered a Barracuda kit from Silverdog, and that may be ok for now, but I'm also considering interfacing to a off-the-shelf metal detector as an alternative. Particularly, I have a Teknetics Gamma 6000 detector, which I like for a couple reasons. The power source for this detector is a single 9V battery, and the battery life if pretty decent. Another positive for this application is the relative open nature of the circuit board. My question is this: The detector appears to have a PIC processor driving a static LCD screen via 4 shift registers (74HC164's). I'd like to interface to the PIC on the serial data side, but I could also interface to the output side of the shift registers. Has anyone interfaced to a detector this way to get at the display data? I will also interface to the buttons fairly easily, which should give me access to the detector's features. One nice thing is the detector always comes up into the same state after power up. No nonvolatile memory settings to deal with on power up. I looked into simply viewing the LCD with a webcam, but for now that doesn't look to viable due to the glare.

        One thing I like about using the off the shelf detector is the ability to have a bunch of ready to go functionality, such as discrimination, ground balancing, all metal mode, pinpointing, etc.

        I will also interface to the audio output of the detector into the PC audio input, and I will be able to sample the audio data using Flowstone's really nice audio capabilities (filtering, manipulation, etc) I hope to use all three interfacing methods (audio, LCD inputs, and buttons inputs) for a pretty decent metal detector susbsystem.

        Any thoughts on this? Anyone else interfaced to an off-the-shelf detector this way?

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        • #19
          I've been looking at the metal detector portion of the rover, and I'd like to get some input.
          This looks like a great project, I own a number of off the shelf MD's that I use at the beach
          and each one has its quirks, just wondering what types you have used on the beach ?
          one good advantage of this rover would be you can operate it in the dark.

          I know of a bunch of guys here in Oz that have a very large coil mounted on the back of
          a ATV they drive it around and drop a marker on the ground for every beep
          then keep going
          and a member of the team then goes to the marker and detects the marker
          for the target.

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          • #20
            I've used the gamma 6000, a whites xlt, a Garrett gti 2500, and an underwater detector I think was a whites PI of some sort. My two favorites were the Garrett and the XLT.

            I intend to use this with my son when we go out. I'll run it a while and he'll digg, then he'll run it and I'll digg. One thing i'm really looking forward to is sampling the audio with the flowstone audio sampling. One good thing about Flowstone is the crazy real time DSP sampling tools. It has fft filters and a spectrum analyzer and oscilloscope tools that might be really cool to play with. By leveraging the PC, I could at least build a really cool GUI.I wish I had the rover frame and locomotion already done because the relay cool stuff will end up being the audio tools I'll be able to play with.

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            • #21
              Sample GUI screen from Flowstone

              Here is a test screenshot of a test GUI using a webcam viewing the LCD screen of the Gamma 6000 with the FFT scope on the audio output channel. The audio unfortunately out of the PIC looks pretty poor. I also have to get a better image, I get a good bit of glare off the LCD. Obviously, I'd rather parse the raw data to the screen, but even after looking at the data stream with a scope, I can't figure out a way to parse it since its just raw data bits.

              One good thing though. I did some tests, and it looks like the first major peak does shift frequency quite a bit with the target ID. This means I can basically use the audio frequency as a discrimination ID.

              The first image shows the FFT of a gold ring, the second shows the FFT of a iron screwdriver. The gold ring first peak is ~450hz, and the iron screwdriver is ~ 100hz.

              Looks promising so far. Keep in mind that FFT is run in real time with the audio. I'll try to video it and post a youtube link later.
              Attached Files

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              • #22
                test GUI if anyone is interested

                I have attached a two part rar archive of the simple GUI, if anyone is interested.

                The GUI defaults to the primary sound card for the FFT input, and the first windows webcam. It should work, but its just a test program. Nice thing is its a standalone exe.

                The start and stop are record buttons, it defaults to C:\video for the video file, so that directory needs to be present in order to work. It only records the wbecam though right now.
                Attached Files

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                • #23
                  Originally posted by 6666 View Post
                  This looks like a great project, I own a number of off the shelf MD's that I use at the beach
                  and each one has its quirks, just wondering what types you have used on the beach ?
                  one good advantage of this rover would be you can operate it in the dark.

                  I know of a bunch of guys here in Oz that have a very large coil mounted on the back of
                  a ATV they drive it around and drop a marker on the ground for every beep
                  then keep going
                  and a member of the team then goes to the marker and detects the marker
                  for the target.
                  Do they use the blanket detector you linked in a couple posts ago? I ordered the barracuda which is a pi design, perhaps I could build a coil into a blanket using that...

                  Comment


                  • #24
                    Found this yesterday. Its similar to what i am looking at doing, except mine will be much larger. The one I will be doing will also be controlled remotely via laptop.

                    http://www.youtube.com/watch?v=Inlc9...yer_embedded#!

                    http://letsmakerobots.com/node/9928

                    Comment


                    • #25
                      Well, I found another type of audio analysis tool. It's a sonogram type. It shows the FFT over time. In the screen capture its the upper right window. The black areas show no item, the white areas show the detected item. This was in all metal mode. I will try to get the spectrogram working later. I found one, but I have yet to figure out how it works.
                      Attached Files

                      Comment


                      • #26
                        I know of a bunch of guys here in Oz that have a very large coil mounted on the back of
                        a ATV they drive it around and drop a marker on the ground for every beep
                        then keep going
                        and a member of the team then goes to the marker and detects the marker
                        for the target.
                        Hi Fix
                        they use the minelab big coil setup, I dont have much more on the blanket coil
                        been looking at the delta pulse setup it uses a 1100x1100 coil, using multi strand
                        wire it would be interesting to try it with a blanket, you have some good stuff going on here
                        keep going.
                        Imagine this on the back of a ATV

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                        • #27
                          Yeah the cool thing is the various components can always be used with something else someone else wants to use, like an ATV.

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                          • #28
                            Originally posted by 6666 View Post
                            Hi Fix
                            they use the minelab big coil setup, I dont have much more on the blanket coil
                            been looking at the delta pulse setup it uses a 1100x1100 coil, using multi strand
                            wire it would be interesting to try it with a blanket, you have some good stuff going on here
                            keep going.
                            Imagine this on the back of a ATV

                            Couple questions. I just got my kit in for the Barracuda Legend. Would this work with a 1100 x 1100 coil? I did some calcs using Qiaozhi's coil calculator, and it looks like with an 1100mm radius, and 16 turns (from the Delta PI schematic), I get and inductance from 2.785mH (30 AWG wire) to 2.378mH (20AWG wire). Does that look right, and will that work with the Barracuda, or should I build the Delta PI?

                            It looks like that with such a large radius, the wire thickness is pretty forgiving. If the coil was deforming (i.e. encapsulated in a blanket) the inductance looks to vary somewhere between 2mH to 4mH. Would this affect tuning, or would I need to build that coil such that it was rigid?

                            As a side note, I have finished rev1 of the BOM for the major components of the rover, and a sketch of the power subsystem. One feature that I had not anticipated at first that might be fairly easy. I will be using RealVNC as the interface between the remote laptop and the onboard PC. It looks like I will also be able to use that with an Android smartphone to control the rover. I will use the wifi built into the phone, and RealVNC, and a virtual router running in the PC. This should allow me to run the rover from my phone if I want. This works really well, I'm quite surprised actually.

                            To get the audio from the metal detector, I will be using VLC to stream the audio from the metal detector to the sound input of the HTPC.

                            I have attached the latest BOM and power subsystem layout in case anyone is interested.
                            Attached Files

                            Comment


                            • #29
                              Originally posted by fixstuff View Post
                              Couple questions. I just got my kit in for the Barracuda Legend. Would this work with a 1100 x 1100 coil? I did some calcs using Qiaozhi's coil calculator, and it looks like with an 1100mm radius, and 16 turns (from the Delta PI schematic), I get and inductance from 2.785mH (30 AWG wire) to 2.378mH (20AWG wire).
                              The coil calculator is designed for circular coils, so you'll need to experiment for a square loop. Also, you asked about an 1100 x 1100 coil, which has a radius of 550mm. Note that the calculator uses the radius, and not the diameter in the calculation.
                              A 550mm radius (circular coil) with 10 turns of 25 AWG (0.455mm) wire has an inductance of 473uH. Is that not closer to what you want?

                              Comment


                              • #30
                                Originally posted by Qiaozhi View Post
                                The coil calculator is designed for circular coils, so you'll need to experiment for a square loop. Also, you asked about an 1100 x 1100 coil, which has a radius of 550mm. Note that the calculator uses the radius, and not the diameter in the calculation.
                                A 550mm radius (circular coil) with 10 turns of 25 AWG (0.455mm) wire has an inductance of 473uH. Is that not closer to what you want?
                                Oh, yeah your right, I missed that. I was thinking diameter for some reason. Do you think that a coil that big would work with the Barracuda? I'd like to use that if I can since I already have the kit.

                                Another question: Does the Barracuda have a non-motion mode? I'd prefer to simply drive over an area without worrying about sweeping a coil back and forth. Not sure if you worked with the Barracuda, but maybe someone else reading this may know also.

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