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My Pulse Oscillation detector project.

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  • #76
    Hi,

    I am interested in this. I am working on a similar design.

    It has good FE discrimination.

    There is frequency shift due to a metal target.
    I believe this is no different to the frequency shift in a PI pulse, or the frequency (not phase) shift in a 'Induction Balance' detector.

    All these technologies do the same thing to a target: Present a changing magnetic field.

    The good thing about a free-running oscillator like this is that the tiny shift in each cycle adds-up (compounds) over time, so if you measure over say 1000 pulses, you get a decent measurable change.

    Another excellent thing is that power is not wasted in a resistor, it is re-used (i.e resonating)

    I believe this style of detector can be more sensitive than any other technology.


    I think:
    To decrease the sensitivity to high resistance targets (wet sand and ferrite) : decrease the frequency.

    Comment


    • #77
      Originally posted by Teemo View Post
      I am currently working at it, to add this feature. Current plan is to make some kind of dual tone sound, so that Ferro NonFerro will make different sounds. I want it to sound something like old times PC speaker music. The information to distinguish is already there, just need to program new sound system.

      Struggling with sound algorithm. I guess I will try to make dual tone sound by switching periodically between audio frequencies. Keep one frequency constant, alter other frequency depending on target.

      Any ideas welcome! If anyone knows a good page about how pc speaker sound was generated for old games, please post link here!
      And why not upgrade the project to another PIC and put a LCD display , headphones output and many other things...
      I could help!! my problem is the assembly language, i only program mplab on C language.

      Seems a very nice project and waiting for parts to test. About the range of the detector it must be worked (find the better coil project), the entire structure construction (wood, PVC).

      Comment


      • #78
        Hi Teemo
        I had a bit of success and good start to your project
        output from pin 2, programmed with Pickit3 and MPLAB IDE 8.76
        Attached Files

        Comment


        • #79
          hello
          i search for some replacements of IRL630
          which is the best one?
          Polarity Struct Pd Uds Ugs Id Tj Fr Cd Rds Caps
          1. 2SK1221 N MOSFET 80 250 30 10 150 0.4 TO220AB
          2. 2SK1761 N MOSFET 75 250 12 0.23 TO220AB
          3. 2SK2841 N MOSFET 80 400 10 TO220AB
          4. 2SK2866 N MOSFET 125 600 10 TO220AB
          5. 2SK900 N MOSFET 80 250 20 12 150 1800 0.3 TO220AB
          6. AUIRFB4127 N MOSFET 375 200 20 76 0.02 TO220AB
          7. AUIRFB4227 N MOSFET 190 200 65 0.026 TO220AB
          8. AUIRFB4332 N MOSFET 390 250 30 60 0.033 TO220AB
          9. AUIRFB4620 N MOSFET 144 200 20 25 0.0725 TO220AB
          10. HIRF630 N MOSFET 74 200 30 9 150 28 240 0.4 TO220AB
          11. IRF630N N MOSFET 82 200 20 9.5 0.3 TO220AB
          12. IRF640N N MOSFET 150 200 20 18 0.15 TO220AB
          13. IRF644 N MOSFET 125 250 10 14 150 0.28 TO220AB
          14. IRFB23N20D N MOSFET 170 200 30 24 0.1 TO220AB
          15. IRFB260N N MOSFET 380 200 20 56 0.04 TO220AB
          16. IRFB31N20D N MOSFET 200 200 30 31 0.082 TO220AB
          17. IRFB38N20D N MOSFET 320 200 30 44 0.054 TO220AB
          18. IRFB4020 N MOSFET 100 200 20 18 0.1 TO220AB
          19. IRFB4127 N MOSFET 375 200 20 76 0.02 TO220AB
          20. IRFB4227 N MOSFET 190 200 30 65 0.026 TO220AB
          21. IRFB4229 N MOSFET 330 250 30 46 0.046 TO220AB
          22. IRFB4233 N MOSFET 370 230 30 56 0.037 TO220AB
          23. IRFB42N20D N MOSFET 300 200 30 42.6 0.055 TO220AB
          24. IRFB4332 N MOSFET 390 250 30 60 0.033 TO220AB
          25. IRFB4620 N MOSFET 144 200 20 25 0.0725 TO220AB
          26. IRFB5620 N MOSFET 144 200 20 25 0.0725 TO220AB
          27. IRL630 N MOSFET 74 200 4.5 9.0 150 0.4 TO220AB
          28. IRL640 N MOSFET 125 200 4.5 17 150 0.18 TO220AB
          29. KF13N50P N MOSFET 208 500 30 13 150 45 210 0.35 TO220AB
          30. KF9N25P N MOSFET 83 250 30 9 150 25 96 0.31 TO220AB
          31. KHB019N20P1 N MOSFET 140 200 30 19 150 33 80 0.14 TO220AB
          32. KHB9D5N20P N MOSFET 87 200 30 9.5 150 62 96 0.345 TO220AB
          33. PHP20NQ20T N MOSFET 150 200 20 0.13 TO220AB
          34. PHP33NQ20T N MOSFET 230 200 32.7 0.077 TO220AB
          35. PSMN057-200P N MOSFET 250 200 39 0.057 TO220AB
          36. PSMN070-200P N MOSFET 250 200 35 0.07 TO220AB
          37. TK13E25D N MOSFET 102 250 13 0.25 SC46/TO220AB
          Über 37 Ergebnisse

          Comment


          • #80
            IRL630

            L = Logic level gate voltages. With "IRL" MOSFETs you can drive it straight from the microprocessor.
            For other MOSFETs you will need to add to schematic MOSFET driver IC or transistor (transistors).

            Comment


            • #81
              As you can see IRL630 can drive several Amperes (ID) with less then 5 Volts on gate (Vgs). It is not so easy to find a replacement.

              Click image for larger version

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              Comment


              • #82
                For IRL630 replacements the priority parameters are:
                -Gate treshold voltage(Vgs): must be less than 4,5V (often called "logic level mosfet")
                -Drain source voltage Vds: must be 200V

                Other project news:
                I have done some testing with the audio, managed to program the variable volume and tone using available resources. Only modification to schematic:It is clear that piezo speaker will not do, instead there will be dynamic speaker or headphones. New sound will use 8 or 10 bit PWM, not clear jet how the modulation will be. I guess the fancy circular buffers from the current version is not good for the new version -- the new algorithm must be simpler. To get the direct unbuffered information from the coil to the headphones/speaker.
                And thanks all who participate in here forums. The tips I get here are most useful, even if I can't grasp all the ideas promptly.

                Comment


                • #83
                  ok
                  thanks for reply
                  i have choosen irl640
                  and some testing replacements for elko 1000 -3300uf 10-16V, the 1uf and the 47nf cap
                  will post results asap

                  kind regards
                  special thanks to teemo

                  Comment


                  • #84
                    detector is alive

                    i used a ferrite core inductivity around 340µH (desoldered from some scrab electronics)
                    i think it should work fine as pinpointer
                    now i search for the smallest 5V power source so that all fits an a small tube enclosure
                    and i will make a better ferrite-coil

                    would say it is the best beginners project in category microcontroller/pinpointer

                    kind regards

                    Comment


                    • #85
                      Originally posted by bernte_one View Post
                      now i search for the smallest 5V power source so that all fits an a small tube enclosure
                      I am not sure will it work from 3.7V (charged 4.2V) 18650 Li-Ion battery. If yes it will be absolutely great because it is compact, rechargeable, lightweight and very powerful 3000-4000 mA/h! Click image for larger version

Name:	3.7V battery 18650 and charger.jpg
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ID:	338130

                      I am using 3 cells starting at full charge 4.2 Volts (12.6 V) and discharging to 3.9 Volts (11.7 V) after 10 hours of work of my overclocked to 130 mA Surf PI.

                      At least microprocessor will work.
                      Operating Voltage Range:
                      - 2.3V-5.5V (PIC12F1840)
                      - 1.8V-3.6V (PIC12LF1840)

                      The problem is IRL640 will work from 4 volts or not also maybe some adjustments are required to software and / or electronic.

                      Comment


                      • #86
                        i think about 18650 bacause i had a lot of them
                        but the have a critical voltage max 4.2 is not enough
                        so my favourite is a small akku pack of 4*1,2V aaa nimh (eneloop?)
                        and a simple charger plug with max charge of 5V usb or micro usb??? - modern standard

                        what do you think?

                        Comment


                        • #87
                          hello teemo

                          can you give me some advice to increase the detection range
                          at the momnt i can get maybe 4cm on a 2€ coin with a pinpointer coil (16mm diameter, 5cm long, litzwire with ferrite core around 80µH)
                          the sound range (from little noise till full sound) is very small maybe 5mm range
                          is it possible to inrease this threshold sound range? a litle bit more noise is no problem if i get two more centimeters of range

                          at which parts should i focus my work?

                          will post a picture later

                          kind regards

                          Comment


                          • #88
                            Originally posted by bernte_one View Post
                            hello teemo

                            can you give me some advice to increase the detection range
                            at the momnt i can get maybe 4cm on a 2€ coin with a pinpointer coil (16mm diameter, 5cm long, litzwire with ferrite core around 80µH)
                            the sound range (from little noise till full sound) is very small maybe 5mm range
                            is it possible to inrease this threshold sound range? a litle bit more noise is no problem if i get two more centimeters of range

                            at which parts should i focus my work?
                            will post a picture later
                            kind regards
                            Hello
                            The solution that comes to mind first is to modify the firmware PIC program. As you very well describe it should be possible to get some more range when to allow some more noise.
                            I've also have had this in mind. The current firmware is very well optimized to my original objective of scanning logs, the digital filtering allows very few noise.
                            This requires quite big modifications to the firmware. Basically the digital filters must be redesigned. In the assembler program there are variables f_result and t_result those are the basic measurements that are passed to the filters in the main program.

                            Best regards and thanks.

                            Comment


                            • #89
                              hello teemo
                              i have to make some experiments with the source code
                              but for the moment lokk what i have done (only prototype)
                              http://www.youtube.com/watch?v=9eG3-gmh7tA

                              if i get more depth by changing the code i will send you the changes if have done
                              and i will post a link on my video to your shop side if that would be ok for you?

                              my goal is to get 2cm for a small nugget and around 8cm for a 2€ coin
                              will see

                              kind regards

                              Comment


                              • #90
                                Hello bernte_one

                                Thank you for the video.
                                Wery interesting construction. Nice to see.
                                I will gladly examine the code changes if you send to me, and of cource I will be happy when you put link to my site in your video.

                                Best regards

                                Comment

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