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My New Pi Metal Detector (ATTiny 25)

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  • #61
    Hi jon-ecm,

    did you get the ground balancing working on your unit?

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    • #62
      It has manual GB but right now the presence of a target is indicated in a tone frequency difference not sound level which has advantages and disadvantages.
      I had good success with using a pwm dac and sending the capacitor averaged output to a VU meter. the only disadvantage being that the meter would bob up and down if it was not held still.

      Basically I've run out of resources on this chip. As it stands now I have been able to hit a nickle at over a foot with a 8" coil in 50% black sand but the lack of proper sound modulation leaves it more of a noisy hybrid pin-pointer.

      This is what has caused me to move to the XPI platform. This new board uses a 16 bit ADC and averages 12 samples taken during the flyback period as well as providing the capability of varying TX length and TX Voltage. Although these features will not be available in anything I release due to patents. The source-code (c) will be made available to encourage development / modification (Although patents must be kept in mind when doing so) at your own risk.


      Jon

      P.S.
      Out of date info on XPI here
      http://www.miymd.com/index.php/projects/xpi/

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      • #63
        I tried burning my first ATtiny25 with Jons code for the TX.
        and it seems to have worked, sort of.

        I used a simple Bascom parallel port burner , its the same as the Dontronics DT006 burner
        and the software was AVR-Burn-o-mat which is a GUI for Avrdude.

        The Hex and fuses all verified, so I am happy about that .

        The result was a positive going pulse 4 milliseconds wide and about 16 milliseconds between the pulses, but by varying the pot which goes to pin 2 does not alter the frequency of the pulses, so got to figure that out.

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        • #64
          If the voltage is changing properly on that pin it's probably a software issue and I will be more than happy to fix it for you, also that hex code on the website is pretty outdated, In later versions I fixed it so the TX would be on for only twice the off time which seemed to work better although it put more drain on the batteries.

          If you know how to program in c I would be happy to share the code with you

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          • #65
            posting sources would be handy if you can email me a copy it would for me be very nice..

            i came across this design on the web and its nice to see some others on a forum to
            share ideas and experiences with

            many thanks for your work so far and keep it up
            i can help making schematics and pcb design if needed

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            • #66
              hallo jonecm please can you post the newest details incl.the newest hexfile from you wonderfull tpimd detector here or on your site i think many people waiting for this update thank you grettings from the harz montains

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              • #67
                Hi Jon
                thanks for the offer,
                would be interesting to have a look at to see if I can learn anything
                from the code.

                I burnt another attiny25
                this one has a positive going pulse
                .5ms wide and about 2ms between pulses
                the pot has no effect.

                the first tiny25 had a positive going pulse 4 milliseconds wide and about 16 milliseconds between the pulses, the pot had no effect.

                I only burnt the flash and fuses on both chips all seemed to verify.

                For the moment if you can post your latest hex that would be very helpfull
                thanks
                cheers

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                • #68
                  Ok, Confirmed I used a different adc input on my board, It should be no issue as I can fix it in software. That would explain why the pot isn't changing the pulse and why the pulse is different on the second chip. I will fix the hex on the website this afternoon if all goes well. I am on vacation right now so I have no way to test but I will do my best to get it right, If you use avr-gcc I can send you the c code if you want to play with it.

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                  • #69
                    Great thanks Jon
                    much appreciated

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                    • #70
                      Thank You JON-ECM

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                      • #71
                        updated TX hex files

                        Updated the hex file for the TX, you can download it here
                        It should be using PB3 (Pin 2) for the adc input now, but I have no way to test as I am currently away.

                        Cheers!
                        Jon

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                        • #72
                          Thanks Jon
                          will burn it now
                          6666

                          I have burned virgin chip #3

                          and the pulse train from pin 6 is about 325 pps
                          the pulse is positive going its about 1.6 milli seconds wide
                          and about 1.6 milli seconds between pulses

                          the pot has no effect on pin 2 (or 3)
                          this is assuming I am doing everything right
                          with the burning process , using same tx fuse values, lf e2, hf dc, ef ff.
                          cheers
                          6666

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                          • #73
                            Originally posted by 6666 View Post
                            I have burned virgin chip #3
                            That almost sounds as if it has lost something
                            You know these chips can be reprogrammed thousands of times right?

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                            • #74
                              Hi jon
                              yes i know they can be reprogrammed
                              but i bought 3 and wanted to be able to compare them
                              tomorrow i will try a shorter parallel cable
                              just in case the signal is a bit low
                              here is the report , says it verified 176 bytes
                              cheers
                              Attached Files

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                              • #75
                                Everything looks good there, It's verified so everything should be good.
                                Is the new hex working?

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