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  • I built one of these last night.


    My disc appeared backwards - all really odd.

    Tx to Rx phase was about 150 deg - tried the old 'swap the Rx coil wires over' trick and it all came in.


    Nice to have a PP - not played with these before, glad to see it works on the 27cm DD.

    As it is it doesnot see small items like small balls of solder, maybe lead shot - which may be a blessing after grubbing thru a palm of soil for an atom of iron with a PI!

    Im running at 7.8kHz (I targeted 8k) to help find smaller items.


    I only have about 20T (0.3mm) on Tx coil and 6v peak to peak
    and about 200T on Rx (0.2mm)

    Crisp Disc, can see difference between rusty iron and steel, Silver booms in fortunately right round to far end. Small roman bronze approx 50 % travel.


    Need to finish this for a farm permission in a couple of weeks.

    S

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    • Hi all,
      Can anybody help me how do I connect my IDX pro to Eduardo's 2 tone board ( all from Silverdog).
      As you can see I'm not a pro

      Lax

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      • perhaps this can help
        Attached Files

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        • This scheme is correct. The former does not. Look at the pin 5 of the CD4024.
          Attached Files

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          • Originally posted by eduardo1979 View Post
            This scheme is correct. The former does not. Look at the pin 5 of the CD4024.
            eduardo1979 Place the file here (lay)

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            • 2 Tones

              That is correct.
              Attached Files

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              • Thanks a lot.
                I've thinked this as well, but I wasn't sure.


                Lax

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                • Geb level

                  With my recent enlightenment - finally understanding operation of things like IDX IGSL.

                  I know that keeping the Geb Ch putput nulled to min is really important.


                  I have a couple of old miniature meters - I want to rig one to the geb output - So I can visually track whats happenning and tweak it down to min - I think this will remove some ambiguity and quickly sets machine up for some hardcore search action..

                  I may need to buffer the GEB Ch - pick off sig where VDI normally does

                  S

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                  • ... and in a process you'll get an all-metal indication. Kinda two flies with one blow. Good thinking.

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                    • sorry, of course. I went there just for the principle of the right connection ....

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                      • Signals from DET

                        Looking at my IDx - it works well... -




                        when waving pliers at it....

                        The Disc/GEB detector signals are opposite is polarity - one up, one down. ?
                        Is this correct?


                        If these signals are going into a common comparator for triggering - both sigs have to 'trip' above threshold (both sig paths are AND - ed together) then the sig polarities should match - so seems wrong?

                        Steve

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                        • pic

                          pic
                          Attached Files

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                          • Originally posted by golfnut View Post
                            when waving pliers at it....

                            The Disc/GEB detector signals are opposite is polarity - one up, one down. ?
                            Is this correct?
                            Yes. IDX and TGSL are single quadrant detectors, and they trigger only for both I (GEB) and Q (Disc) channels going positive (in this particular case, and that particular spot it must be both negative, the inverting gain stages take care of that). If you reverse inputs of the lowest comparator, you'll get a Fe discriminating rig.

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                            • In recent dicussion the Comparator stage on IDX was described as an AND function - having satisfied the amplitude requirement with both channels being over the common threshold.

                              When I look at this part of the circuit I see an OR arrangement. As either comp OP will trip tone..!

                              So Im lost here..


                              If One comparator output was High and the other low - the +dc OP would go thru the diode and put tone ON ...

                              Or is it the case that if one output is Hi while the other comparator output is low - The Low condition output sinks the HI from the other CH?

                              So both would need to be Hi.

                              Again I apologise for the dumbness

                              S

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